godan verb (-mu), intransitive verb
slip in for sex; shack up with
Slangy, often used for sneaking into a lover's place, a hotel, or a red-light district for sexual purposes.
彼は彼女のアパートにしけこんだ。
He slipped into his girlfriend's apartment for sex.
週末はいつもラブホにしけこんでるらしい
Apparently they shack up at a love hotel every weekend.
godan verb (-mu), intransitive verb
shut oneself away at home (due to lack of money)
Rare, colloquial use; implies hiding at home because one is broke and cannot go out.
金がなくて、週末はずっと家にしけこんでた。
I had no money, so I just shut myself away at home all weekend.