Illegitimate \Il`le*git"i*mate\, a.

1. Not according to law; not regular or authorized; unlawful; improper.

2. Unlawfully begotten; born out of wedlock; bastard; as, an illegitimate child.

3. Not legitimately deduced or inferred; illogical; as, an illegitimate inference.

4. Not authorized by good usage; not genuine; spurious; as, an illegitimate word.

Illegitimate fertilization, or Illegitimate union (Bot.), the fertilization of pistils by stamens not of their own length, in heterogonously dimorphic and trimorphic flowers. --Darwin.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Illegitimate \Il`le*git"i*mate\, v. t. [imp. & p. p. Illegitimated; p. pr. & vb. n. Illegitimating.]

To render illegitimate; to declare or prove to be born out of wedlock; to bastardize; to illegitimatize.

The marriage should only be dissolved for the future, without illegitimating the issue. --Bp. Burnet.

Source: Webster's Revised Unabridged Dictionary (1913)