The Collaborative International Dictionary of English v.0.48:

Subservient \Sub*serv"i*ent\, a. [L. subserviens, -entis, p. pr.
   See Subserve.]
   Fitted or disposed to subserve; useful in an inferior
   capacity; serving to promote some end; subordinate; hence,
   servile, truckling.
   [1913 Webster]

         Scarce ever reading anything which he did not make
         subservient in one kind or other.        --Bp. Fell.
   [1913 Webster]

         These ranks of creatures are subservient one to
         another.                                 --Ray.
   [1913 Webster]

         Their temporal ambition was wholly subservient to their
         proselytizing spirit.                    --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

subservient
    adj 1: compliant and obedient to authority; "editors and
           journalists who express opinions in print that are
           opposed to the interests of the rich are dismissed and
           replaced by subservient ones"-G. B. Shaw
    2: serving or acting as a means or aid; "instrumental in solving
       the crime" [syn: implemental, instrumental,
       subservient]
    3: abjectly submissive; characteristic of a slave or servant;
       "slavish devotion to her job ruled her life"; "a slavish yes-
       man to the party bosses"- S.H.Adams; "she has become
       submissive and subservient" [syn: slavish, subservient,
       submissive]

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "subservient":
   abject, accepting, accessory, acquiescent, adjuvant, agential,
   agentival, agentive, agreeable, ancillary, appurtenant, assenting,
   assistant, assisting, auxiliary, base, client, collateral, common,
   complaisant, compliable, compliant, complying, conducive,
   consenting, contributory, cowering, cringing, crouching,
   deferential, demeaning, dependent, disadvantaged, employable,
   facilitating, favoring, fawning, feudal, feudatory, forwarding,
   fostering, handy, helpful, helping, humble, ignoble, in the shade,
   inferior, infra dig, instrumental, intermediary, junior, less,
   lesser, liege, low, lower, lowly, mean, mediating, mediatorial,
   menial, ministerial, ministering, ministrant, minor, modest,
   nondissenting, nonresistant, nonresisting, nonresistive, nurtural,
   nutricial, obedient, obeisant, obsequious, on bended knee,
   ordinary, passive, promoting, prone, prostrate, resigned,
   second rank, second string, secondary, serviceable, servile,
   serving, slavish, sub, subaltern, subject, submissive, subordinate,
   subsidiary, supine, third rank, third string, tributary, truckling,
   unassertive, uncomplaining, underprivileged, unresistant,
   unresisting, useful, vassal, vulgar