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.
雨の日は靴の中がムレムレになる。
On rainy days, the inside of my shoes gets all steamy and sweaty.
この部屋、ムレムレで暑いね。
This room is so stuffy and hot, isn't it?
ジメジメ describes a damp, wet, and often gloomy humidity, while ムレムレ emphasizes the warm, steamy, and sweaty discomfort.
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.