The Collaborative International Dictionary of English v.0.48:

Ignoble \Ig*no"ble\, a. [L. ignobilis; pref. in- not + nobilis
   noble: cf. F. ignoble. See In- not, and Noble, a.]
   1. Of low birth or family; not noble; not illustrious;
      plebeian; common; humble.
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            I was not ignoble of descent.         --Shak.
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            Her royal stock graft with ignoble plants. --Shak.
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   2. Not honorable, elevated, or generous; base.
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            'T is but a base, ignoble mind,
            That mounts no higher than a bird can soar. --Shak.
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            Far from the madding crowd's ignoble strife. --Gray.
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   3. (Zool.) Not a true or noble falcon; -- said of certain
      hawks, as the goshawk.

   Syn: Degenerate; degraded; mean; base; dishonorable;
        reproachful; disgraceful; shameful; scandalous;
        infamous.
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The Collaborative International Dictionary of English v.0.48:

Ignoble \Ig*no"ble\, v. t.
   To make ignoble. [Obs.] --Bacon.
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WordNet (r) 3.0 (2006):

ignoble
    adj 1: completely lacking nobility in character or quality or
           purpose; "something cowardly and ignoble in his
           attitude"; "I think it a less evil that some criminals
           should escape than that the government should play an
           ignoble part"- Oliver Wendell Holmes, Jr. [ant: noble]
    2: not of the nobility; "of ignoble (or ungentle) birth";
       "untitled civilians" [syn: ignoble, ungentle, untitled]