windfall profit vs net profit

windfall profit and net profit both are nouns.

Word	Noun	Adjective	Verb	Adverb
windfall profit	Yes	No	No	No
net profit	Yes	No	No	No

As nouns, net profit is a hypernym of windfall profit; that is, net profit is a word with a broader meaning than windfall profit:

windfall profit: profit that occurs unexpectedly as a consequence of some event not controlled by those who profit from it
net profit: the excess of revenues over outlays in a given period of time (including depreciation and other non-cash expenses)

Other hypernyms of windfall profit include earnings, lucre, net, net income, profit, profits.

windfall profit (noun)	net profit (noun)
profit that occurs unexpectedly as a consequence of some event not controlled by those who profit from it	the excess of revenues over outlays in a given period of time (including depreciation and other non-cash expenses)