Source : Webster's Revised Unabridged Dictionary (1913)

Illegitimately \Il`le*git"i*mate*ly\, adv.
   In a illegitimate manner; unlawfully.

Source : WordNet®

illegitimately
     adv 1: in a manner disapproved or not allowed by custom; "He acted
            illegitimately when he increased the rent fourfold"
            [syn: {illicitly}] [ant: {legitimately}, {legitimately}]
     2: of biological parents not married to each other; "this child
        was born illegitimately" [syn: {out of wedlock}] [ant: {legitimately}]