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.
Civil Engineering.
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.
Origin: 1300–50;Middle Englishtrestel < Middle French, by dissimilation from Old Frenchtrestre ≪ Latintrānstrum crossbeam
early 14c., "a support for something," from O.Fr. trestel "crossbeam" (12c.), presumed to be an alteration of L. *transtellum, dim. of transtrum "beam, crossbar." Specific meaning "support for a bridge" is recorded from 1796.