·superl Moist; damp; moldy; as, muggy straw.
II. Muggy ·superl Warm, damp, and close; as, muggy air, weather.
moist ; muggy weather. North. ...
A glossary of provincial and local words used in England by Francis Grose
Half intoxicated. A sheet in the wind. Also used to express damp, oppressive weather. ...
The Sailor's Word-Book