scrunch vs sit down

scrunch is a noun but sit down is not a noun.

Word	Noun	Adjective	Verb	Adverb
scrunch	Yes	No	Yes	No
sit down	No	No	Yes	No

As verbs, sit down is a hypernym of scrunch; that is, sit down is a word with a broader meaning than scrunch:

scrunch: sit on one's heels
sit down: be in a position in which one's upper body is largely upright and supported by one's backside

Other hypernyms of scrunch include sit.

scrunch (noun)	sit down (noun)
a crunching noise

scrunch (verb)	sit down (verb)
make wrinkles or creases on a smooth surface; make a pressed, folded or wrinkled line in; `crisp' is archaic	show to a seat; assign a seat for
sit on one's heels	be in a position in which one's upper body is largely upright and supported by one's backside
make a noise typical of an engine lacking lubricants	take a seat