burst forth vs flower

burst forth is not a noun while flower is a noun.

Word	Noun	Adjective	Verb	Adverb
burst forth	No	No	Yes	No
flower	Yes	No	Yes	No

As verbs, flower is a hypernym of burst forth; that is, flower is a word with a broader meaning than burst forth:

Other hypernyms of burst forth include bloom, blossom.

burst forth (noun)	flower (noun)
	a plant cultivated for its blooms or blossoms
	reproductive organ of angiosperm plants especially one having showy or colorful parts
	the period of greatest prosperity or productivity

burst forth (verb)	flower (verb)
be unleashed; emerge with violence or noise	produce or yield flowers
come into or as if into flower
jump out from a hiding place and surprise (someone)