grass vs tell on

grass is a noun but tell on is not a noun.

Word	Noun	Adjective	Verb	Adverb
grass	Yes	No	Yes	No
tell on	No	No	Yes	No

As verbs, grass and tell on are synonyms defined as:

Other synonyms of grass include betray, denounce, give away, rat, shit, shop, snitch, stag.

grass (noun)	tell on (noun)
street names for marijuana
bulky food like grass or hay for browsing or grazing horses or cattle
a police informer who implicates many people
narrow-leaved green herbage: grown as lawns; used as pasture for grazing animals; cut and dried as hay

grass (verb)	tell on (verb)
give away information about somebody	produce an effect or strain on somebody
shoot down, of birds	give away information about somebody
feed with grass
cover with grass
spread out clothes on the grass to let it dry and bleach