adverb, adverb taking the 'to' particle
irresistibly; suddenly; welling up
Mimetic adverb describing a strong urge or feeling that arises suddenly and uncontrollably. Often used with ～と or ～する to describe impulses.
彼の話を聞いて、むらむらと怒りがこみ上げてきた。
Hearing his story, anger welled up inside me irresistibly.
むらむらと好奇心が湧いて、つい覗いてしまった。
Curiosity suddenly surged up and I couldn't help but peek.
noun or participle which takes 'suru'
get turned on; feel horny
Colloquial use, often as むらむらする, describing a sudden surge of sexual desire. Can be used by any gender.
彼女のセクシーな姿を見て、むらむらしてきた。
Seeing her sexy figure, I started to feel turned on.
一人でいると、むらむらすることもある。
Sometimes when I'm alone, I get horny.