biscuit vs drop biscuit

biscuit and drop biscuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
biscuit	Yes	No	No	No
drop biscuit	Yes	No	No	No

As nouns, drop biscuit is a hyponym of biscuit; that is, drop biscuit is a word with a more specific, narrower meaning than biscuit:

biscuit: small round bread leavened with baking-powder or soda
drop biscuit: biscuit made from dough with enough milk that it can be dropped from a spoon

biscuit (noun)	drop biscuit (noun)
small round bread leavened with baking-powder or soda	biscuit made from dough with enough milk that it can be dropped from a spoon
any of various small flat sweet cakes