illegitimate
il-le-git-i-mate
adjective
Not authorised by law, rules, or logic; unlawful or improper.
"Their claim was illegitimate."
adjective
(Of a child) born to parents not legally married to each other.
"He was an illegitimate son."
Thesaurus
Synonyms: adulterine, left-handed, misbegot, wrongful, bastardly, base, misbegotten, fatherless, spurious, unlawful, baseborn, love child
Antonyms: legitimate