Green’s Dictionary of Slang

1. (US) great in size, quantity, significance or achievement.

1917		in J.R. McConnell Flying for France 55: Now and then monster projectiles hurtling through the air close by leave one’s plane rocking violently in their wake.
1923		Chicago Defender 22 Sept. 5: All the Chicago musicians, music lovers and friends are anxiously awaiting the great musicale [...] Dr. Wm. D. Cook will welcome the monster crowd.
1930		(con. WW1) P.A. Rockwell American Fighters in the Foreign Legion 200: The Escadrille protected a monster bombing raid across the Rhine on October 12, and took part in an aerial battle in which hundreds of Allied and German planes were engaged.
1937		Jennings & Madge May the Twelfth: Mass-Observation Day-Surveys 3:83: ‘Biggest blaze I’ve seen’ (it certainly is a monster blaze).
1967		W. Murray Sweet Ride 89: They’re throwing a monster blast over on East Latego.
1973		C. Gaines Stay Hungry 145: I just shot it up and sat there laughing at this spade I was with while I had this monster flash, like creamin off in my head.
1984		J. Ellroy Because the Night 18: He [...] pulls out a monster hand-cannon and demands the money.
1992		G. Wolff ‘Waterway’ in A Day at the Beach (1992) 229: She’d seen some twenty-year-old carrying around a monster load of worry and bad luck.
1999		J. Poller Reach 111: I find Patricia chopping up monster lines of whizz with her Barclaycard.
2005		D. Jenkins Slim & None 188: [He] sank a monster putt for a par.

2. (US black) annoying, irritating.

1953

L. Durst Jives of Dr. Hepcat (1989) 4: I wish that chick in zero position refrain from chewing gum and making with the floorshow! You know it’s most monster when you are trying to dig the happenings and all of a sudden everybody acts like a P-80 take off.

3. (US black) excellent, first-rate, the very best.

1972		B. Rodgers Queens’ Vernacular 210: monster weed superb marijuana.
1988		D. Woodrell Muscle for the Wing 88: It’s a flat-out monster drink.
1994		N. McCall Makes Me Wanna Holler (1995) 125: This is monster herb.
2012		S. Blass Pirate for Life 134: [A] monster game from Bob Robertson, who hit three home runs and a double and drove in five runs.