rag vs brush down

rag is a noun but brush down is not a noun.

Word	Noun	Adjective	Verb	Adverb
rag	Yes	No	Yes	No
brush down	No	No	Yes	No

As verbs, brush down is a hyponym of rag; that is, brush down is a word with a more specific, narrower meaning than rag:

Other hyponyms of rag include castigate, chasten, chastise, correct, objurgate, tell off.

rag (noun)	brush down (noun)
a boisterous practical joke (especially by college students)
a small piece of cloth
newspaper with half-size pages
music with a syncopated melody (usually for the piano)
a week at British universities during which side-shows and processions of floats are organized to raise money for charities

rag (verb)	brush down (verb)
break into lumps before sorting	reprimand
censure severely or angrily
harass with persistent criticism or carping
play in ragtime
treat cruelly
cause annoyance in; disturb, especially by minor irritations