bow down vs bob

bow down is not a noun while bob is a noun.

Word	Noun	Adjective	Verb	Adverb
bow down	No	No	Yes	No
bob	Yes	No	Yes	No

bow down (noun)	bob (noun)
	a short abrupt inclination (as of the head)
	a short or shortened tail of certain animals
	a small float usually made of cork; attached to a fishing line
	a hanging weight, especially a metal ball on a string
	a long racing sled (for 2 or more people) with a steering mechanism
	a hair style for women and children; a short haircut all around
	a former monetary unit in Great Britain

bow down (verb)	bob (verb)
bend one's knee or body, or lower one's head	cut hair in the style of a bob
get into a prostrate position, as in submission	make a curtsy; usually done only by girls and women; as a sign of respect
	remove or shorten the tail of an animal
	move up and down repeatedly in a quick, short movement
	ride a bobsled