dress down vs lecture

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

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

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

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

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