crop up vs burst out

crop up and burst out both are verbs.

Word	Noun	Adjective	Verb	Adverb
crop up	No	No	Yes	No
burst out	No	No	Yes	No

As verbs, crop up and burst out are synonyms defined as:

crop up and burst out: appear suddenly or unexpectedly; happen unexpectedly

Other synonyms of crop up include pop, pop out, pop up.

crop up (verb)	burst out (verb)
appear suddenly or unexpectedly; happen unexpectedly	erupt or intensify suddenly
	give sudden release to an expression
	appear suddenly or unexpectedly; happen unexpectedly