lecture vs brush down

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

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

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

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

lecture (noun)	brush down (noun)
teaching by giving a discourse on some subject (typically to a class)
a speech that is open to the public
a lengthy rebuke

lecture (verb)	brush down (verb)
censure severely or angrily	reprimand
deliver a lecture or talk