To Crack Up

1. To laugh.
   1. (idiomatic, intransitive) To laugh heartily.
   2. (idiomatic, transitive) To cause to laugh heartily.
   3. (slang, intransitive) To tease (someone) or tell jokes at the expense of (someone).
2. To break.
   1. (idiomatic, intransitive, dated in US) To become insane; to suffer a mental breakdown.
   2. (idiomatic) To break down or fall apart; to stop functioning; to shatter.
   3. (idiomatic, transitive) To separate a group.
   4. (US) To crash an aircraft or automobile.
   5. (transitive) To remove the shell from nuts.
   6. (transitive) To crack (petroleum). (to break down (a complex molecule), especially with the application of heat: to pyrolyse*)
3. To affect the image of something.
   1. (slang, transitive) To praise or applaud (something); to promote a positive view of (something).
   2. (dated, transitive) To insult, demean or harm the image of (something).
   3. (transitive, informal, usually passive voice, chiefly in the negative) To cry up; to extol.
4. (slang, intransitive) To smoke crack cocaine.