slam vs flap down

slam is a noun but flap down is not a noun.

Word	Noun	Adjective	Verb	Adverb
slam	Yes	No	Yes	No
flap down	No	No	Yes	No

As verbs, slam and flap down are synonyms defined as:

slam (noun)	flap down (noun)
an aggressive remark directed at a person like a missile and intended to have a telling effect
winning all or all but one of the tricks in bridge
a forceful impact that makes a loud noise
the noise made by the forceful impact of two objects