Green’s Dictionary of Slang

1. drunk.

1821		‘An Amateur’ Real Life in London I 449: All of them rather muggy.
1853		Dickens ‘Slang’ in Household Words 24 Sept. 75/2: For the one word drunk [...] muggy, beery, winey, slewed [etc.].
1862		W. Cheadle Journal (1931) 30 Nov. 89: Indians still drunk; La Ronde all right; Bruneau muggy.
1873		Sl. Dict.
1895		E. Townsend Chimmie Fadden Explains 19: Pretty soon he was so muggy in his little head [...] and I was just tankin him along till he was clean dead t’ de woild.
1906		Salt Lake City (UT) 30 Mar. 4/5: He is [...] muggy, [...] swipey, podgy, cock-eyed .
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 215: muggy, drunk.
1997		Share Slanguage.

2. (drugs) causing unpleasant feelings of sweatiness and stupor.

1979

H. Feldman et al. Angel Dust 125: When I smoke rocket fuel [...] It’s muggy. I get that effects that it’s dirty. I sweat more and I’m more apt to black out.