slammer vs holding cell

slammer and holding cell both are nouns.

Word	Noun	Adjective	Verb	Adverb
slammer	Yes	No	No	No
holding cell	Yes	No	No	No

As nouns, holding cell is a hyponym of slammer; that is, holding cell is a word with a more specific, narrower meaning than slammer:

slammer: a correctional institution used to detain persons who are in the lawful custody of the government (either accused persons awaiting trial or convicted persons serving a sentence)
holding cell: a jail in a courthouse where accused persons can be confined during a trial

Other hyponyms of slammer include bastille, hoosegow, hoosgow, house of correction, lockup, workhouse.

slammer (noun)	holding cell (noun)
a correctional institution used to detain persons who are in the lawful custody of the government (either accused persons awaiting trial or convicted persons serving a sentence)	a jail in a courthouse where accused persons can be confined during a trial
a person who closes things violently