pulley vs bullock block

pulley and bullock block both are nouns.

Word	Noun	Adjective	Verb	Adverb
pulley	Yes	No	No	No
bullock block	Yes	No	No	No

As nouns, bullock block is a hyponym of pulley; that is, bullock block is a word with a more specific, narrower meaning than pulley:

pulley: 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
bullock block: a pulley-block at the head of a topmast

Other hyponyms of pulley include bollock, fairlead, idle pulley, idle wheel, idler pulley.

pulley (noun)	bullock block (noun)
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 pulley-block at the head of a topmast