n. 25B6; noun
a crack in the glass : SPLIT, break, chip, fracture, rupture; crazing.
a crack between two rocks : SPACE, gap, crevice, fissure, cleft, breach, rift, cranny, chink, interstice.
the crack of a rifle : BANG, report, explosion, detonation, pop; clap, crash.
a crack on the head : BLOW, bang, hit, knock, rap, punch, thump, bump, smack, slap; informal bash, whack, thwack, clout, wallop, clip, biff, bop.
(informal) we'll have a crack at it : ATTEMPT, try; informal go, shot, stab, whack; formal essay.
(informal) cheap cracks about her clothes : JOKE, witticism, quip; jibe, barb, taunt, sneer, insult; informal gag, wisecrack, funny, dig.
25B6; verb
the glass cracked in the heat : BREAK, split, fracture, rupture, snap.
she cracked him across the forehead : HIT, strike, smack, slap, beat, thump, knock, rap, punch; informal bash, whack, thwack, clobber, clout, clip, wallop, belt, biff, bop, sock; Brit. informal slosh; N. Amer. informal boff, bust, slug.
the witnesses cracked : BREAK DOWN, give way, cave in, go to pieces, crumble, lose control, yield, succumb.
(informal) the naval code proved harder to crack : DECIPHER, interpret, decode, break, solve, resolve, work out, find the key to; informal figure out, suss out.
25B6; adjective a crack shot : EXPERT, skilled, skilful, formidable, virtuoso, masterly, consummate, excellent, first-rate, first-class, marvellous, wonderful, magnificent, outstanding, superlative; deadly; informal great, superb, fantastic, ace, hotshot, mean, demon; Brit. informal brilliant; N. Amer. informal crackerjack.
incompetent.
25A0; crack down on SUPPRESS, prevent, stop, put a stop to, put an end to, stamp out, eliminate, eradicate; clamp down on, get tough on, come down hard on, limit, restrain, restrict, check, keep in check, control, keep under control.
25A0; crack up (informal) BREAK DOWN, have a breakdown, lose control, go to pieces, go out of one's mind, go mad; informal lose it, fall/come apart at the seams, go crazy, freak out.