Nouns

(n)bastard, by-blow, love child, illegitimate child, illegitimate, whoresonthe illegitimate offspring of unmarried parents

Adjectives

(a)illegitimateof marriages and offspring; not recognized as lawful
(s)illegitimate, illicit, outlaw, outlawed, unlawfulcontrary to or forbidden by law“an illegitimate seizure of power”, “illicit trade”, “an outlaw strike”, “unlawful measures”