The Collaborative International Dictionary of English v.0.48:

Kowtow \Kow*tow"\, v. i. [imp. & p. p. Kowtowed; p. pr. & vb.
   n. Kowtowing.]
   To perform the kowtow. Same as Kotow
   [1913 Webster]

         I have salaamed and kowtowed to him.     --H. James.
   [1913 Webster]

   2. To defer to another in a servile or humiliating manner; to
      act obsequiously.

   Syn: kotow.
        [PJC]