WordNet sense 1 (two items of the same kind):

brace, couple, couplet, duet, duo, pair, twain, twosome, yoke, distich, duad, dyad

WordNet sense 2 (a structure that allows people or vehicles to cross an obstacle such as a river or canal or railway etc.):

bridge

WordNet sense 3 (to cover or extend over an area or time period):

cross, sweep, traverse

WordNet sense 4 (the act of sitting or standing astride):

straddle