The Collaborative International Dictionary of English v.0.48:

Submissive \Sub*mis"sive\, a.
   1. Inclined or ready to submit; acknowledging one's
      inferiority; yielding; obedient; humble.
      [1913 Webster]

            Not at his feet submissive in distress,
            Creature so fair his reconcilement seeking.
                                                  --Milton.
      [1913 Webster]

   2. Showing a readiness to submit; expressing submission; as,
      a submissive demeanor.
      [1913 Webster]

            With a submissive step I hasted down. --Prior.
      [1913 Webster]

   Syn: Obedient; compliant; yielding; obsequious; subservient;
        humble; modest; passive.
        [1913 Webster] -- Sub*mis"sive*ly, adv. --
        Sub*mis"sive*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

submissive
    adj 1: inclined or willing to submit to orders or wishes of
           others or showing such inclination; "submissive
           servants"; "a submissive reply"; "replacing troublemakers
           with more submissive people" [ant: domineering]
    2: 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:

171 Moby Thesaurus words for "submissive":
   abject, abused, accepting, accommodating, accordant, acquiescent,
   acquiescing, adaptable, adapting, adaptive, adjustable, adjusting,
   affirmative, agreeable, agreed, agreeing, amenable, approving,
   ass-kissing, assentatious, assenting, base, bendable, bending,
   biddable, bow, bring, browbeaten, brown-nosing, capitulate, cave,
   complaisant, compliable, compliant, complying, conceding,
   concessive, conformable, conforming, consentient, consenting,
   content, defer, deferential, deliver, devoted, docile, domestic,
   domesticated, downtrod, downtrodden, ductile, duteous, dutiful,
   eager, elastic, endorsing, extensible, extensile, fabricable,
   facile, faithful, favorable, fictile, flexible, flexile, flexuous,
   formable, formative, giving, ground down, hand in, henpecked,
   humble, humble-minded, humble-spirited, humblehearted, impressible,
   impressionable, in leading strings, ingratiating, knuckle,
   knuckle under, law-abiding, like putty, limber, lissome, lithe,
   lithesome, loyal, malleable, manageable, mean, meek, meek-minded,
   meek-spirited, meekhearted, menial, misused, moldable,
   nondissenting, nonresistant, nonresisting, nonresistive,
   nothing loath, obedient, obeisant, obeying, obsequious, offer,
   on bended knee, oppressed, ordered around, other-directed,
   overborne, passive, permissive, plastic, pliable, pliant,
   poor in spirit, present, proffer, prompt, prostrate, ratifying,
   ready, receptive, reconciled, refer, regimented, resigned,
   responsive, sanctioning, send, sensitive, sequacious, servile,
   shapable, slavish, springy, subdued, submit, subservient, succumb,
   supine, supple, surrender, susceptible, sycophantic, tender, timid,
   toadying, tractable, tractile, trampled, truckling, tyrannized,
   unassertive, uncomplaining, ungrudging, unloath, unmanned,
   unrefusing, unreluctant, unresistant, unresisting, whippy, willing,
   willowy, yielding