good luck vs fluke

good luck and fluke both are nouns.

Word	Noun	Adjective	Verb	Adverb
good luck	Yes	No	No	No
fluke	Yes	No	No	No

As nouns, good luck and fluke are synonyms defined as:

Other synonyms of good luck include good fortune.

good luck (noun)	fluke (noun)
an unexpected piece of good luck	parasitic flatworms having external suckers for attaching to a host
a stroke of luck	either of the two lobes of the tail of a cetacean
an auspicious state resulting from favorable outcomes	flat bladelike projection on the arm of an anchor
	a barb on a harpoon or arrow
	a stroke of luck