Noun, Suru verb
intravaginal (anal, etc.) ejaculation; creampie
Vulgar expression or wordalso jokingly as 中田氏see 外出し
ただし、安全日だからって、中出ししても妊娠しないというわけではないらしいです。However, it seems that just because it's a 'low risk day' doesn't mean that you won't get pregnant from intravaginal ejaculation.
Also written 中だし【なかだし】