keep back vs block

keep back is not a noun while block is a noun.

Word	Noun	Adjective	Verb	Adverb
keep back	No	No	Yes	No
block	Yes	No	Yes	No

As verbs, block is a hyponym of keep back; that is, block is a word with a more specific, narrower meaning than keep back:

Other hyponyms of keep back include freeze, immobilise, immobilize, keep to oneself, deny, reserve, immobilise, immobilize, deprive.

keep back (noun)	block (noun)
	the act of obstructing or deflecting someone's movements
	a solid piece of something (usually having flat rectangular sides)
	an obstruction in a pipe or tube
	a simple machine consisting of a wheel with a groove in which a rope can run to change the direction or point of application of a force applied to the rope
	a metal casting containing the cylinders and cooling ducts of an engine
	a platform from which an auctioneer sells
	housing in a large building that is divided into separate units
	an inability to remember or think of something you normally can do; often caused by emotional tension
	a number or quantity of related things dealt with as a unit
	a rectangular area in a city surrounded by streets and usually containing several buildings
	(computer science) a sector or group of sectors that function as the smallest data unit permitted
	a three-dimensional shape with six square or rectangular sides

keep back (verb)	block (verb)
prevent the action or expression of	shape into a block or blocks
hold back; refuse to hand over or share	shape by using a block
secure and keep for possible future use or application	prohibit the conversion or use of (assets)
	be unable to remember
	interfere with or prevent the reception of signals
	impede the movement of (an opponent or a ball)
	render unsuitable for passage
	obstruct
	stamp or emboss a title or design on a book with a block
	support, secure, or raise with a block
	block passage through
	shut out from view or get in the way so as to hide from sight
	interrupt the normal function of by means of anesthesia
	hinder or prevent the progress or accomplishment of
	stop from happening or developing
	run on a block system