off-the-peg vs ready-to-wear

off-the-peg is not a noun while ready-to-wear is a noun.

Word	Noun	Adjective	Verb	Adverb
off-the-peg	No	Yes	No	No
ready-to-wear	Yes	Yes	No	No

As adjectives, off-the-peg and ready-to-wear are synonyms defined as:

off-the-peg and ready-to-wear: (especially of clothing) made in standard sizes and available from merchandise in stock

Other synonyms of off-the-peg include off-the-rack, off-the-shelf.

off-the-peg (noun)	ready-to-wear (noun)
	ready-made clothing

off-the-peg (adjective)	ready-to-wear (adjective)
(especially of clothing) made in standard sizes and available from merchandise in stock	(especially of clothing) made in standard sizes and available from merchandise in stock