Definition of "muggy"

The next was a very unpropitious morning for a journey—muggy, damp, and drizzly.

1836 March – 1837 October, Charles Dickens, chapter XXXV, in The Posthumous Papers of the Pickwick Club, London: Chapman and Hall, […], published 1837

What struck me as the most curious thing about this wonderful river was: how did the air keep fresh? It was muggy and thick, no doubt, but still not sufficiently so to render it bad or even remarkably unpleasant.

1887, H[enry] Rider Haggard, chapter X, in Allan Quatermain‎

The evening, though sunless, had been warm and muggy for the season, and Tess had come out with her milking-hood only, naked-armed and jacketless; certainly not dressed for a drive.

1891, Thomas Hardy, chapter XXIX, in Tess of the d’Urbervilles: A Pure Woman Faithfully Presented […], volumes (please specify |volume=I to III), London: James R[ipley] Osgood, McIlvaine and Co., […]

Muggy heat—temperature in the 90s and high humidity—greeted early arrivals for the 72-hole, three-day test, rated the hardest and most important in the sport.

1964 June 16, “All Eyes On Lema At U.S. Open This Week”, in The Indianapolis Star, volume 62, number 11, Indianapolis, Ind., page 22