tamp vs tamp down

tamp is a noun but tamp down is not a noun.

Word	Noun	Adjective	Verb	Adverb
tamp	Yes	No	Yes	No
tamp down	No	No	Yes	No

As verbs, tamp and tamp down are synonyms defined as:

Other synonyms of tamp include pack.

tamp (noun)	tamp down (noun)
a tool for tamping (e.g., for tamping tobacco into a pipe bowl or a charge into a drill hole etc.)

tamp (verb)	tamp down (verb)
press down tightly	press down tightly