illegitimate

adjective

1 illegitimate share trading:

illegal, unlawful, illicit, against the law, criminal, lawbreaking, actionable, felonious;

unlicensed, unauthorized, unsanctioned, unwarranted, unofficial;

banned, forbidden, barred, prohibited, outlawed, interdicted, proscribed, not allowed, not permitted, against the rules;

contraband, black-market, under the counter, bootleg;

fraudulent, corrupt, dishonest, dishonourable;

German verboten;

Law malfeasant;

informal crooked, shady;

British, informal bent, dodgy.

▷antonyms legitimate, lawful.

2 an illegitimate child:

born out of wedlock, born of unmarried parents;

love;

dated born on the wrong side of the blanket, unfathered;

archaic bastard, natural, misbegotten, baseborn, spurious, nameless;

rare adulterine.

▷antonyms legitimate.

3 it is quite illegitimate to treat such a person as a swindler:

incorrect, illogical, invalid, unsound, spurious, wrongly inferred, wrongly deduced.

▷antonyms legitimate, correct.

illegitimate Oxford Dictionary of English