The Collaborative International Dictionary of English v.0.48:

Humble \Hum"ble\ (h[u^]m"b'l; 277), a. [Compar. Humbler
   (h[u^]m"bl[~e]r); superl. Humblest (h[u^]m"bl[e^]st).] [F.,
   fr. L. humilis on the ground, low, fr. humus the earth,
   ground. See Homage, and cf. Chameleon, Humiliate.]
   1. Near the ground; not high or lofty.
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            Thy humble nest built on the ground.  --Cowley.
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   2. Not pretentious or magnificent; unpretending; unassuming;
      modest; as, a humble cottage. Used to describe objects.
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   3. Thinking lowly of one's self; claiming little for one's
      self; not proud, arrogant, or assuming; thinking one's
      self ill-deserving or unworthy, when judged by the demands
      of God; lowly; weak; modest. Used to describe people.
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            God resisteth the proud, but giveth grace unto the
            humble.                               --Jas. iv. 6.
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            She should be humble who would please. --Prior.
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            Without a humble imitation of the divine Author of
            our . . . religion we can never hope to be a happy
            nation.                               --Washington.
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   Humble plant (Bot.), a species of sensitive plant, of the
      genus Mimosa (Mimosa sensitiva).

   To eat humble pie, to endure mortification; to submit or
      apologize abjectly; to yield passively to insult or
      humiliation; -- a phrase derived from a pie made of the
      entrails or humbles of a deer, which was formerly served
      to servants and retainers at a hunting feast. See
      Humbles. --Halliwell. --Thackeray.
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WordNet (r) 3.0 (2006):

humble plant
    n 1: prostrate or semi-erect subshrub of tropical America, and
         Australia; heavily armed with recurved thorns and having
         sensitive soft grey-green leaflets that fold and droop at
         night or when touched or cooled [syn: sensitive plant,
         touch-me-not, shame plant, live-and-die, humble
         plant, action plant, Mimosa pudica]