Green’s Dictionary of Slang

1. clumsy, ineffective, incompetent.

1929		W.R. Burnett Little Caesar (1932) 162: Colonna, once a ham prize-fighter, was a small bull-necked man with a battered, dark face.
1930		J.T. Farrell ‘Twenty-five Bucks’ in Short Stories (1937) 184: He made money out of a string of ham scrappers.
1946		G. Gibson Enemy Coast Ahead (1955) 38: What a ham effort!

2. theatrical, melodramatic.

1920		R. Lardner Big Town 152: Besides the Janes and the fat rascals with them, you seen a flock of ham actors.
1930		W.R. Burnett Iron Man 196: Too damn many ham actors to suit me.
1941		B. Schulberg What Makes Sammy Run? (1992) 42: I grabbed it up from a ham actor who bought it on the strength of a contract he was going to get.
1952		M. Millar Vanish in an Instant (2016) 17: ‘Put on an act [...] Ham or not’.
1958		Willans & Searle Complete Molesworth (1985) 16: Wot a ham performance i’m giving.
1969		N. Cohn Awopbop. (1970) 14: He’d pull out every last outrageous ham trick in the book.
1978		R. Price Ladies’ Man (1985) 163: She never said ‘My love’ like that, like a ham actress.
1989		T. Blacker Fixx 309: Squaring his shoulders like an old ham actor.
1999		Guardian Guide 12–18 June 95: A ham actor standing in for his indisposed lawyer pal.