rat vs grass

rat and grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
rat	Yes	No	Yes	No
grass	Yes	No	Yes	No

As nouns, grass is a hyponym of rat; that is, grass is a word with a more specific, narrower meaning than rat:

rat: one who reveals confidential information to the police or other authority
grass: a police informer who implicates many people

As verbs, rat and grass are synonyms defined as:

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

rat (noun)	grass (noun)
any of various long-tailed rodents similar to but larger than a mouse	street names for marijuana
a pad (usually made of hair) worn as part of a woman's coiffure	bulky food like grass or hay for browsing or grazing horses or cattle
a person who is deemed to be despicable or contemptible	a police informer who implicates many people
someone who works (or provides workers) during a strike	narrow-leaved green herbage: grown as lawns; used as pasture for grazing animals; cut and dried as hay
one who reveals confidential information to the police or other authority

rat (verb)	grass (verb)
give away information about somebody	give away information about somebody
catch rats, especially with dogs	shoot down, of birds
give (hair) the appearance of being fuller by using a rat	feed with grass
desert one's party or group of friends, for example, for one's personal advantage	cover with grass
take the place of work of someone on strike	spread out clothes on the grass to let it dry and bleach
employ scabs or strike breakers in