chat up vs mash

chat up is not a noun while mash is a noun.

Word	Noun	Adjective	Verb	Adverb
chat up	No	No	Yes	No
mash	Yes	No	Yes	No

As verbs, chat up and mash are synonyms defined as:

Other synonyms of chat up include butterfly, coquet, coquette, dally, flirt, philander, romance.

chat up (noun)	mash (noun)
	mixture of ground animal feeds
	a mixture of mashed malt grains and hot water; used in brewing

chat up (verb)	mash (verb)
talk or behave amorously, without serious intentions	reduce to small pieces or particles by pounding or abrading
talk to someone with the aim of persuading him	talk or behave amorously, without serious intentions
	to compress with violence, out of natural shape or condition