crack up - definition and synonyms

phrasal verb informal
present tense
I/you/we/theycrack up
he/she/itcracks up
present participlecracking up
past tensecracked up
past participlecracked up
  1. 1
    [intransitive] to become mentally ill

    He just cracked up from the stress.

  2. 2
    [intransitive] to suddenly laugh a lot at something

    The girls all cracked up when they saw him.

    1. a.
      [transitive] crack someone up to make someone laugh a lot

      Little kids just crack me up with the things they say.

  3. 3
    something is not all it’s cracked up to be used for saying that something is not as good as people say that it is
     Synonyms and related words
See also main entry: crack