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a. the disposal of merchandise at reduced prices
b. (as modifier): a clearance sale
2. the act of clearing an area of land of its inhabitants by mass eviction
3. Dentistry the extraction of all of a person's teeth
4. a less common word for clearing
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the maximum profile of an object. As applied to transport vehicles and the moving parts of stationary machines, clearance is determined on the basis of their safe movement among other machines and structures. Outside the clearance, which permits the movement of machines in different directions, it is possible to erect structures and set up machines, lathes, and the safety zone for people. For example, the clearance of a moving train is the maximum profile in a plane perpendicular to the axis of the railway track beyond which no part of a locomotive or car should project when in working order. A railway clearance gauge is the maximum profile in a plane perpendicular to the axis of the railway track within which no parts of structures and equipment should extend. Meeting these clearances ensures the safe movement of trains in tunnels, on bridges, and under over-bridges. Underbridge clearance is the profile of the clear opening under a bridge between the bottom of its span structure and the estimated navigable level in height and between the supports of the span in width.


Evgrafov, G. K., and N. N. Bogdanov. Proektirovanie mostov. Moscow, 1966.
Evgrafov, G. K., and N. N. Bogdanov. Zheleznye dorogi. Moscow, 1968.
Evgrafov, G. K., and N. N. Bogdanov. AvtomobiV. Ekspluatatsiia i remont. Entsiklopedicheskii slovar’-spravochnik. Moscow, 1968.




the distance from ground level (plane of reference) to the lowest structural member of a motor vehicle, excluding the wheels; one of the parameters that determine the operational trafficability of motor vehicles.

The minimum permissible clearances established in the USSR are 200 mm, 240 mm, 260 mm, and 270 mm for fully loaded trucks with carrying capacities of 1.5 tons, 3 tons, 5 tons, and 8-12 tons, respectively, and 240-270 mm for buses, depending on their length and purpose.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


Unobstructed space required for occasional removal of parts of equipment.
(mechanical engineering)
In a piston-and-cylinder mechanism, the space at the end of the cylinder when the piston is at dead-center position toward the end of the cylinder.
The ratio of the volume of this space to the piston displacement during a stroke.
(mining engineering)
The space between the top or side of a car and the roof or wall.
The clear space between a vessel and an object such as a navigation light, hazard to navigation, or another vessel.
A specific message from air-traffic control to a pilot of an aircraft allowing him to proceed in accordance with the flight plan which the pilot had filed, or with some modification of the original plan.
In the instrument landing system, the difference in the depth of modulation which is required to produce a full-scale deflection of the course deviation indicator needle in any flight sector outside the on-course sectors.
Elevation of a gun at such an angle that a projectile will not strike an obstacle between the muzzle and the target.
(petroleum engineering)
The annular space between down-hole drill-string equipment, such as bits, core barrels, and casing, and the walls of the borehole with the down-hole equipment centered in the hole.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1. Open space between two elements of a building to aid in proper placement, to compensate for minor inaccuracies in cutting, or to allow unobstructed movement between parts.
2. The space or distance allowed for anchorage or erection processes or to accommodate dimensional variations in the building structure.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

air traffic control clearance

Authorization for an aircraft to proceed under conditions specified by an air traffic control unit (ICAO). This is to prevent collisions between known aircraft. The pilot-in-command of an aircraft must not deviate from the provisions of VFR (visual flight rules) or IFR (instrument flight rules) air traffic clearance except in an emergency or unless an amended clearance has been obtained. Additionally, the pilot may request a different clearance if he or she has information available that makes another course of action more practical or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued. Pilots may also request clarification or amendment, as appropriate, any time a clearance is not fully understood or is considered unacceptable because of safety. Controllers should, in any such instance and to the extent of operational practicality and safety, honor the pilot's request. The pilot is responsible for requesting an amended clearance if ATC issues a clearance that would cause him or her to deviate from a rule or regulation, or, in the pilot's opinion, would place the aircraft in jeopardy. Normally, only the word clearance is used, and it may be prefixed by words such as start-up, taxi, takeoff, departure, approach, or landing to indicate the particular portion of flight to which the ATC clearance relates. Also called an air traffic clearance.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
The 58 patients treated with the vehicle cream had a mean 33.4% reduction in lesions, and 3.4% had total clearance, he said.
But it was in the second frame that the Scot wrote his name in the record books, his superb total clearance the first ever to be compiled in a ranking tournament in Asia.
Maguire (left) made his stunning total clearance in the second frame - the first ever in a ranking tournament in Asia.
The world No.2 chalked up a brilliant 141 total clearance during a sparkling 6-4 win over Stephen Lee - just days after arriving in Dublin faced with the prospect of losing his top-16 status.
They give full support to the arrow and they all but disappear after the shot for total clearance. This serves two main accuracy-enhancing functions.
But Wilson reeled off the last five frames and weighed in with a 142 total clearance, equalling the tournament's highest break.
Gray, a regular practice partner of Jimmy White, rounded off his latest victory with a 130 total clearance after earlier breaks of 50, 89 and 60 had fired him 3-1 ahead.
O'Sullivan stormed back from a 5-2 deficit to beat Neil Robertson 9-5, wrapping up victory in style with a total clearance of 141.
The Rocket's total clearance came in the last frame of his last-16 clash in York against former practice partner Selt.
A total clearance of 141 in the final frame of the afternoon session carried him into a 5-3 lead at the break in their all-Essex tussle at the Crucible, a match O'Sullivan has revealed could be his last before retiring.
"Practice has gone well and it's paid off in the first match." Maguire made three centuries in the match, including a total clearance of 127 in the final frame.
A 130 total clearance was Hendry's emphatic response for 3-3 before Selby made it 4-3 by snatching a dramatic seventh frame on the black.

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