'ham it up' definitions:

Definition of 'ham it up'

(from WordNet)
verb
Exaggerate one's acting [syn: overact, ham it up, ham, overplay] [ant: underact, underplay]

Definition of 'ham it up'

From: GCIDE
  • Ham \Ham\ (h[a^]m), v. i. (Theater) To act with exaggerated voice and gestures; to overact. [PJC]
  • ham it up to act in a showy fashion or to act so as to attract attention; to ham. [Colloq.] [PJC]