I. adjective
1.
not recognized by law as lawful offspring
an illegitimate child
Synonyms: baseborn, bastard, fatherless, misbegotten, natural, spurious, supposititious, unfathered
Related Word: birthless; adulterine
Antonyms: legitimate
2.
Synonyms: unlawful , criminal, illegal, illicit, lawless, wrongful
Antonyms: legitimate
II. noun
Synonyms: bastard 1, by-blow, catch colt, chance child, come-by-chance, filius nullius, filius populi, love child, natural child, woods colt
Antonyms: legitimate