notch
[näch] (electronics)
Rectangular depression extending below the sweep line of the radar indicator in some types of equipment.
(engineering)
A V-shaped indentation or cut in a surface or edge.
(geology)
A deep, narrow cut near the high-water mark at the base of a sea cliff.
(geography)
A narrow passage between mountains or through a ridge, hill, or mountain.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.