The Collaborative International Dictionary
Bow compasses
Compasses \Com"pass*es\, n., pl. An instrument for describing circles, measuring figures, etc., consisting of two, or (rarely) more, pointed branches, or legs, usually joined at the top by a rivet on which they move.
Note: The compasses for drawing circles have adjustable pen points, pencil points, etc.; those used for measuring without adjustable points are generally called dividers. See Dividers.
Bow compasses. See Bow-compass.
Caliber compasses, Caliper compasses. See Calipers.
Proportional, Triangular, etc., compasses. See under Proportional, etc.
Wiktionary
bow compasses
n. (bow compass English)