1 balls (taboo slang) ballsiness (taboo slang) bottle (Brit. slang) bravery, coolness, courage, daring, determination, endurance, energy, face (informal) fearlessness, firmness, force, fortitude, gameness, grit, guts (informal) hardihood, intrepidity, mettle, might, pluck, resolution, spirit, spunk (informal) steadfastness, vigour, will
2 (informal) audacity, boldness, brass (informal) brass neck (Brit. informal) brazenness, cheek (informal) chutzpah (U.S. & Canad. informal) effrontery, front, gall, impertinence, impudence, insolence, neck (informal) sassiness (U.S. slang) sauce (informal) temerity vb
3 brace, embolden, encourage, fortify, hearten, invigorate, steel, strengthen