protrude vs bulk

protrude is not a noun while bulk is a noun.

Word	Noun	Adjective	Verb	Adverb
protrude	No	No	Yes	No
bulk	Yes	No	Yes	No

As verbs, bulk is a hyponym of protrude; that is, bulk is a word with a more specific, narrower meaning than protrude:

protrude (noun)	bulk (noun)
	the property of something that is great in magnitude
	the property resulting from being or relating to the greater in number of two parts; the main part
	the property possessed by a large mass

protrude (verb)	bulk (verb)
swell or protrude outwards	cause to bulge or swell outwards
bulge outward	stick out or up
extend out or project in space	to gain size and weight by means of exercise and diet