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

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

WordNet sense 2 (elastic straps that hold trousers up (usually used in the plural)):

suspender, gallus

WordNet sense 3 (an appliance that corrects dental irregularities):

braces, orthodontic braces

WordNet sense 4 (a carpenter's tool having a crank handle for turning and a socket to hold a bit for boring):

bitstock

WordNet sense 5 (a structural member used to stiffen a framework):

bracing

WordNet sense 6 (prepare (oneself) for something unpleasant or difficult):

poise, poise

WordNet sense 7 (support or hold steady and make steadfast, with or as if with a brace):

stabilize, steady, stabilise

WordNet sense 8 (cause to be alert and energetic):

arouse, energize, stimulate, energise, perk up