incest Meaning, Definition & Usage

  1. noun sexual intercourse between persons too closely related to marry (as between a parent and a child)

WordNet

In"cest noun
Etymology
F. inceste, L. incestum unchastity, incest, fr. incestus unchaste; pref. in- not + castus chaste. See Chaste.
Definitions
  1. The crime of cohabitation or sexual commerce between persons related within the degrees wherein marriage is prohibited by law. Shak.

Webster 1913