lecture vs dress down

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

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

As verbs, lecture and dress down are synonyms defined as:

lecture (noun)	dress 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)	dress down (verb)
censure severely or angrily	dress informally and casually
deliver a lecture or talk	censure severely or angrily