The Collaborative International Dictionary of English v.0.48:

Obsequious \Ob*se"qui*ous\, a. [L. obsequiosus, fr. obsequium
   compliance, fr. obsequi, fr. obsequi: cf. F. obs['e]quieux,
   See Obsequent, and cf. Obsequy.]
   1. Promptly obedient, or submissive, to the will of another;
      compliant; yielding to the desires of another; devoted.
      [Obs.]
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            His servants weeping,
            Obsequious to his orders, bear him hither.
                                                  --Addison.
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   2. Servilely or meanly attentive; compliant to excess;
      cringing; fawning; as, obsequious flatterer, parasite.
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            There lies ever in "obsequious" at the present the
            sense of an observance which is overdone, of an
            unmanly readiness to fall in with the will of
            another.                              --Trench.
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   3. [See Obsequy.] Of or pertaining to obsequies; funereal.
      [R.] "To do obsequious sorrow." --Shak.
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   Syn: Compliant; obedient; servile. See Yielding.
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WordNet (r) 3.0 (2006):

obsequious
    adj 1: attempting to win favor from influential people by
           flattery [syn: bootlicking, fawning, obsequious,
           sycophantic, toadyish]
    2: attentive in an ingratiating or servile manner; "obsequious
       shop assistants"