adverb, noun which may take the genitive case particle 'no'
Describes a hot, humid, and stuffy feeling, often from trapped steam or sweat. Used for clothes, rooms, or body parts that feel uncomfortably damp and warm.
On rainy days, the inside of my shoes gets all steamy and sweaty.
This room is so stuffy and hot, isn't it?
Kanji spelling is possible but very uncommon; the word is usually written in kana.
Reduplication of the verb stem 蒸れ (mure, 'steaming, becoming stuffy'), creating a mimetic-like adverb/adjective emphasizing a state of being filled with steam or sweat.