The Collaborative International Dictionary of English v.0.48:

Deferential \Def`er*en"tial\, a. [See Deference.]
   Expressing deference; accustomed to defer.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "deferential":
   accommodating, affable, agreeable, attentive, cap in hand,
   ceremonious, civil, complaisant, conscientious, considerate,
   courteous, crouching, disarming, duteous, dutiful, ethical, fair,
   graceful, gracious, honorific, insinuating, insinuative, moral,
   obedient, obeisant, obliging, obsequious, observant,
   on bended knee, polite, prone, prostrate, regardful, respectful,
   saccharine, scrupulous, servile, silken, silky, solicitous,
   subservient, tactful, thoughtful, urbane