Synonyms for Kowtow (same or very similar meaning)
WordNet sense 1 (a former Chinese custom of touching the ground with the forehead as a sign of respect or submission):
kotow
WordNet sense 2 (bend the knees and bow in a servile manner):
genuflect, scrape
WordNet sense 3 (try to gain favor by cringing or flattering):
fawn, toady, truckle, bootlick, suck up
From the ODE community, based on WordNet
add/edit