noun, noun or participle which takes 'suru'
Slang term, likely derived from the onomatopoeic phrase ギシギシアンアン (creaking and moaning sounds associated with sexual activity). Used informally.
See also: ギシギシアンアン
昨日彼女とギシアンした。
I had sex with my girlfriend yesterday.
あの二人、またギシアンしてるよ。
Those two are at it again.