kowtow

Short definition from Wiktionary

Verb

1. 1
   To kneel and bow low enough to touch one’s forehead to the ground.
2. 2
   To grovel, act in a very submissive manner; to show obeisance to (someone or something) in such a manner; to bow.
3. 3
   To bow very deeply.

Noun

1. 1
   The act of kowtowing.