What is "mamzer"

Mamzer \Mam"zer\, n. [Heb. m['a]mz[=e]r.] A person born of relations between whom marriage was forbidden by the Mosaic law; a bastard.
--Deut. xxiii. 2 (Douay version).

"bastard," 1560s, from Late Latin mamzer, from Hebrew mamzer, left untranslated in Deut. xxiii:2 in the Vulgate.

n. 1 a child who is born out of wedlock, from an incestuous relationship or from parents of different faiths; a bastard 2 a contemptible person, a jerk

A mamzer is a person born from certain forbidden relationships, or the descendant of such a person, in the Hebrew Bible and Jewish religious law. A mamzer in modern Jewish culture is someone who is either born of adultery by a married Jewish woman and a Jewish man who is not her husband, or born of incest (as defined by the Bible), or someone who has a mamzer as a parent. Mamzer status is not synonymous with illegitimacy, since it does not include children whose mothers were unmarried.