The Collaborative International Dictionary of English v.0.48:

Sycophantic \Syc`o*phan"tic\, Sycophantical \Syc`o*phan"tic*al\,
   a. [Cf. Gr. ? slanderous.]
   Of or pertaining to a sycophant; characteristic of a
   sycophant; meanly or obsequiously flattering; courting favor
   by mean adulation; parasitic.
   [1913 Webster]

         To be cheated and ruined by a sycophantical parasite.
                                                  --South.
   [1913 Webster]

         Sycophantic servants to the King of Spain. --De
                                                  Quincey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sycophantic
    adj 1: attempting to win favor from influential people by
           flattery [syn: bootlicking, fawning, obsequious,
           sycophantic, toadyish]
    2: attempting to win favor by flattery [syn: bootlicking,
       fawning, sycophantic, toadyish]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "sycophantic":
   abject, adulatory, backscratching, beggarly, bland, blandishing,
   blarneying, bootlicking, buttery, cajoling, complimentary,
   courtierly, courtly, cowering, crawling, cringing, crouching,
   fair-spoken, fawning, fine-spoken, flattering, footlicking,
   fulsome, groveling, gushing, hangdog, honey-mouthed, honey-tongued,
   honeyed, ingratiating, insincere, insinuating, kowtowing,
   mealymouthed, obeisant, obsequious, oily, oily-tongued,
   on bended knee, parasitic, prostrate, slimy, slobbery, smarmy,
   smooth, smooth-spoken, smooth-tongued, sniveling, soapy,
   soft-soaping, sponging, timeserving, toadeating, toadying,
   toadyish, truckling, unctuous, wheedling