Green’s Dictionary of Slang

1. one who is in charge, a leader, a boss.

1935		Ted Yates This Is New York 5 Apr. [synd. col.] The Apollo em-cee is getting too much around the waist’.
1938		P. Grey ‘’Twixt Night ’n’ Dawn’ in Afro-American (Baltimore, MD) 5 Nov. 11/3: Harrison Owens, popular m.c., is back [...] as master of ceremonies and manager.
1941		‘Digg Mee’ ‘Observation Post’ in N.Y. Age 12 Apr. 9/7: Les Petites Femes [sic] (the Little Women) are giving another fine affair [...] Ben (do you know him?) Anderson is the emcee.
1951		Green & Laurie Show Biz from Vaude to Video 61: Even with James J. Morton as its m.c., it failed to click.
1952		Lait & Mortimer USA Confidential 230: The blue material of a fat female emcee was what farmhands repeat behind the silo.
1965		K. Marlowe Mr Madam (1967) 126: Blue Baby, an MC-singer at a club in the French Quarter.
1972		D. Jenkins Semi-Tough 133: Some phony fuckin’ emcee thought that stunt up.
1997		L. Davies Candy 78: Being MC, I was first diver off the block.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 326: Tran played MC. Tran dropped kadre bios — all last names di di.
2021		J. Ellroy Widespread Panic 87: Jimmy played emcee. ‘Claire, this is Freddy, Freddy this is Claire’.

2. attrib. use of sense 1.

1952

L. Hughes Laughing to Keep from Crying 29: ‘We can’t use that M.C. outfit you got on,’ he said, talking about the tux.

3. (orig. US black) the lead singer of a rap band; e.g. M.C. Noise.

1987		in N. George ‘Rakin and Eric B.’ in Buppies, B-Boys, Baps and Bohos (1994) 79: I take seven MC’s, put them in a line.
1988		Ice-T ‘Heartbeat’ 🎵 Make it or break it, although most emcees do fake it.
1998		Hip-Hop Connection Dec. 8: But that’s a million miles away from criticising an emcee’s music.
2000		W. Shaw Westsiders 46: He was the first [DJ] to have his own crew of MCs — the artists who would later become known as ‘rappers’, rhyming over the beats.