Crack  —n. 1 a sharp explosive noise. B sudden harshness or change in vocal pitch. 2 sharp blow. 3 a narrow opening; break or split. B chink. 4 colloq. Joke or malicious remark. 5 colloq. Attempt. 6 slang crystalline form of cocaine broken into small pieces. —v. 1 break without separating the parts. 2 make or cause to make a sharp explosive sound. 3 break with a sharp sound. 4 give way or cause to give way (under torture etc.). 5 (of the voice) change pitch sharply; break. 6 colloq. Find the solution to. 7 tell (a joke etc.). 8 colloq. Hit sharply. 9 (as cracked adj.) Crazy. 10 break (wheat) into coarse pieces. —attrib. Adj. Colloq. Excellent; first-rate (crack shot).  crack a bottle open a bottle, esp. Of wine, and drink it. Crack down on colloq. Take severe measures against. Crack of dawn daybreak. Crack up colloq. 1 collapse under strain. 2 praise. Get cracking colloq. Begin promptly and vigorously. [old english]