2,223. Defining a Chalalah
Hilchos Issurei Biah 19:1
A chalalah is a woman born from relationships that are prohibited to kohanim. Additionally, any woman who is prohibited to kohanim and who engages in intimacy with a kohein is rendered a chalalah. A kohain who violates in such a manner, however, is not rendered a chalal.
Hilchos Issurei Biah 19:2
The previous halacha applies even if the woman participated in such relations under duress or unintentionally. It applies equally to “regular” (i.e., vaginal) or “irregular” intercourse; the woman is rendered a chalalah as soon as the kohein’s organ enters so long as he’s at least nine years and a day old and she’s at least three years and a day old.