Pronunciation: (tres'ul), [key]
1. a frame typically composed of a horizontal bar or beam rigidly joined or fitted at each end to the top of a transverse A-frame, used as a barrier, a transverse support for planking, etc.; horse.
2. Civ. Engin.
a. one of a number of bents, having sloping sides of framework or piling, for supporting the deck or stringers of a bridge.
b. a bridge made of these.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.