The Collaborative International Dictionary of English v.0.48:

Misbehave \Mis`be*have"\, v. t. & i. [imp. & p. p. Misbehaved;
   p. pr. & vb. n. Misbehaving.]
   To behave ill; to conduct one's self improperly; -- often
   used with a reciprocal pronoun.
   [1913 Webster]

WordNet (r) 3.0 (2006):

misbehave
    v 1: behave badly; "The children misbehaved all morning" [syn:
         misbehave, misconduct, misdemean] [ant: behave,
         comport]