The Collaborative International Dictionary of English v.0.48:

bootlicker \bootlicker\ n.
   someone who humbles himself as a sign of respect; who behaves
   as he had no self-respect.

   Syn: apple polisher, bootlick, fawner, groveller, truckler,
        ass-kisser, toady.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

bootlicker
    n 1: someone who humbles himself as a sign of respect; who
         behaves as if he had no self-respect [syn: apple
         polisher, bootlicker, fawner, groveller, groveler,
         truckler]