The Collaborative International Dictionary of English v.0.48:

Kotow \Ko*tow"\, n. [Chinese, knock head.]
   Same as kowtow, the more common spellings. [China] [Also
   spelled kowtow.] --S. W. Williams.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Kotow \Ko*tow"\, v. i. [imp. & p. p. Kotowed; p. pr. & vb. n.
   Kotowing.]
   1. To perform the kotow. Now usually spelled kowtow. [Also
      spelled kowtow.]
      [1913 Webster]

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

The Collaborative International Dictionary of English v.0.48:

Kowtow \Kow*tow"\, n. [Chinese, knock head.]
   The prostration made by mandarins and others to their
   superiors, either as homage or worship, by knocking the
   forehead on the ground; same as Kotow. There are degrees in
   the rite, the highest being expressed by three knockings.
   [China] [Also spelled kotow.] --S. W. Williams.
   [1913 Webster]

WordNet (r) 3.0 (2006):

kotow
    n 1: a former Chinese custom of touching the ground with the
         forehead as a sign of respect or submission [syn: kowtow,
         kotow]
    v 1: try to gain favor by cringing or flattering; "He is always
         kowtowing to his boss" [syn: fawn, toady, truckle,
         bootlick, kowtow, kotow, suck up]