run around vs lark

run around is not a noun while lark is a noun.

Word	Noun	Adjective	Verb	Adverb
run around	No	No	Yes	No
lark	Yes	No	Yes	No

As verbs, run around and lark are synonyms defined as:

Other synonyms of run around include cavort, disport, frisk, frolic, gambol, lark about, rollick, romp, skylark, sport.

run around (noun)	lark (noun)
	any carefree episode
	any of numerous predominantly Old World birds noted for their singing
	a songbird that lives mainly on the ground in open country; has streaky brown plumage
	North American songbirds having a yellow breast

run around (verb)	lark (verb)
play boisterously	play boisterously