B2 [ T or I ] to break something so that it does not separate, but very thin lines appear on its surface, or to become broken in this way:

[ I ] informal to become mentally and physically weak:

[ I ] informal to fail as a result of problems:

[ I ] If someone cracks, that person begins to feel weak and agrees that they have been defeated:

[ T ] to break something open, especially in order to reach or use what is inside:

[ T ] also crack into sth to get into someone else's computer system without permission and get information or do something illegal

[ T ] informal to copy computer programs or recorded material illegally

[ T ] to find a solution to a problem:

[ I or T, usually + adv/prep ] to hit something or someone:

[ I or T ] to make a sudden, short noise, or to cause something to make this noise:

[ I ] If a voice cracks, its sound changes because the person is upset:

C1 [ T ] to make a joke or funny remark:

C2 [ C ] a very narrow space between parts of something:

[ C ] a sudden loud sound:

[ C usually singular ] informal an attempt:

[ U ] also crack cocaine slang a powerful form of the drug cocaine:

[ U ] →  craic

[ C ] informal a method of getting into someone else's computer system:

[ C ] a wisecrack

excellent, or of the highest quality: