definition of
crack

[1] #1 crack v. [check, break] become fractured; break or crack on the surface only; "The glass cracked when it was heated". wn

[2] #2 crack v. make a very sharp explosive sound; "His gun cracked". wn

[3] #3 crack n. [cleft, crevice, fissure, scissure] a long narrow opening. wn

[4] #4 crack s. [ace, A-one, first-rate, super, tiptop, topnotch, top-notch, tops] of the highest quality; "an ace reporter"; "a crack shot"; "a first-rate golfer"; "a super party"; "played top-notch tennis"; "an athlete in tiptop condition"; "she is absolutely tops". wn

[5] #5 crack n. [gap] a narrow opening; "he opened the window a crack". wn