pop up vs burst out

pop up and burst out both are verbs.

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

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

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

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

pop 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