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river, 80 mi (129 km) long, rising in three forks in the Sierra Nevada, uniting N of Oroville, Calif., and flowing S into the Sacramento River, N of Sacramento, Calif. The Feather River basin was a rich source of gold in the mid-1800s. The Feather River project (1957–68), which includes Oroville Dam, furnishes central and S California with water and provides flood control, recreation, and hydroelectricity in the river basin.


A specialized keratinous outgrowth of the skin, which is a unique characteristic of birds. Feathers are highly complex structures that provide insulation, protection against mechanical damage, and protective coloration, and also function significantly in behavior. One special functional role is in flight, where feathers provide propulsive surfaces and a body surface aerodynamically suitable for flight. Feathers are used in maintenance of balance and occasionally in the capture of prey and various specialized displays.

Types of feathersenlarge picture
Types of feathers

A representative definitive feather contains a single long central axis which supports a row of small branchlike structures along each side (barbs). Barbs form the vane, or web, of the feather. Individual barbs branch off at variable angles and point toward the outer tip of the feather. The barbules are small branches from the barbs. They lie in the same plane as the barbs and arise in rows from their anterior and posterior surfaces. The anterior barbules have a flattened base and a series of small hooklike projections which attach to the proximal ridge of the posterior barbules of the next barb, forming an interlocking structure characterized by its great strength and light weight. All feather types consist basically of these structural elements.

Most of the superficial feathers are contour feathers (pennae). These include the large flight feathers (remiges) of the wing and the long tail feathers (rectrices). Other common feather types include the down feathers (plumulae), intermediate types (semiplumes), and filoplumes (see illustration).

Feathers normally undergo attrition because of the physical abuse attendant to the normal activity of birds. In most species, feathers are replaced completely at least annually, and many of the feathers are replaced more frequently. The sequence of feather molt is surprisingly orderly. Penguins, which shed large patches of feathers in an irregular pattern, are an exception. In most species the power of flight is retained during molt. The molt, that is, the normal shedding of feathers and their replacement by a new generation of feathers, is a single growth process which is actively concerned only with the production of the new generation of feathers. The old feathers are pushed out of the follicles passively.

A major physiological role of feathers is to provide insulation. This is accomplished by regulating the configuration of feather and skin in such a way that differing amounts of air are trapped in the dead space so formed. A second mechanism for control of heat dissipation is the balance of the exposure of feathered and unfeathered body parts.

Feathers act as a protective boundary in their role of providing waterproofing. Water repellency is a structural feature of feathers and is the result of precise geometric relationships between the diameter and spacing of barbs and barbules. Preening appears to be more important in the maintenance of this structure than it is for the application of oils or any other natural product, as was once thought.

A third function of the surface configuration and overall pattern of feathers is in the area of behavioral adaptations. These may be of two types. First is concealment, when the bird is cryptically marked to match its background and escape detection. The second type consists of various types of advertisement. See Protective coloration



one of the horny epidermal formations of birds. Feathers cover most of a bird’s body, forming its plumage. There are various kinds of feathers: contour feathers, filoplumes, down feathers, powder downs, and bristles.

The contour feathers have the most complex contruction. They consist of a shaft and two vanes. The lower part of the shaft, the calamus, is hollow and has no vanes. The remaining part of the shaft, the rachis, is solid and consists of a light, horny, alveolate tissue. The vanes are comprised of long barbs that are interlocked by barbules. The contour feathers include the flight feathers, which play a major role in the formation of the supporting surfaces of the wings; the rectrices, which form the tail; and the covert feathers, which cover the trunk of the bird and a substantial part of the wings. In most birds the covert feathers do not entirely cover the bird’s body: feathered areas, or pterylae, alternate with bare areas, or apteria.

Filoplumes consist of a long, slender, rachis that is soft and has very few barbs at the distal end. They are usually hidden by the contour feathers, but in some birds, such as cormorants, they emerge to the surface at the neck and back of the head. Down feathers are characterized by a slender shaft and soft barbs that do not interlock. Both down feathers and powder downs protect the body from cold. The powder downs consist of a soft shaft and dissociated barbs. The juvenile feather, from which all types of feathers develop, is similar to a powder down. Bristles consist of shafts that lack barbs. It is conjectured that they, like filoplumes, perform a tactile function.

Because feathers wear out and fade at the tips, they must be periodically replaced, or molted. Feathers are used for filling beds, pillows, and upholstered furniture, as well as for making warm clothing (eiderdown is especially valuable).


What does it mean when you dream about a feather?

Feathers carry all of the connotations of birds. Additionally, because they were traditionally used in pillows and down coats, they can represent softness and warmth. Finally, because of the dreaming mind’s tendency to literalize verbal expressions, feathers can symbolize lightness (“light as a feather”) and certain associations (“birds of a feather”).


(mechanical engineering)
To change the pitch on a propeller in order to reduce drag and prevent windmilling in case of engine failure.
(vertebrate zoology)
An ectodermal derivative which is a specialized keratinous outgrowth of the epidermis of birds; functions in flight and in providing insulation and protection.


1. In joinery, a projection (tongue) on the edge of a board which fits into the groove of another board, as in a tongue and groove. Also called a spline.
2. To produce a featheredge.

spline, false tongue, feather, slip feather, slip tongue

spline, 2
spline, 1
1. A long thin strip of wood or metal which is inserted in a slot formed by two members, each of which is grooved and butted against the other.
2. In a suspended acoustical ceiling, a strip of metal or hard fiber inserted in the slot between adjacent acoustical tiles which butt against each other, forming a concealed mechanical joint.


Position of propeller at various stages of operations.
i. The rotation of a helicopter rotor blade about its pitch-change axis.
ii. Turning propeller blades to a feathering angle to minimize drag and prevent further damage that could lead to engine failure.


1. any of the flat light waterproof epidermal structures forming the plumage of birds, each consisting of a hollow shaft having a vane of barbs on either side. They are essential for flight and help maintain body temperature
2. Archery
a. a bird's feather or artificial substitute fitted to an arrow to direct its flight
b. the feathered end of an arrow, opposite the head
3. Nautical the wake created on the surface of the water by the raised periscope of a submarine
4. Rowing the position of an oar turned parallel to the water between strokes
5. a step in ballroom dancing in which a couple maintain the conventional hold but dance side by side