parlay vs double up

parlay is a noun but double up is not a noun.

Word	Noun	Adjective	Verb	Adverb
parlay	Yes	No	Yes	No
double up	No	No	Yes	No

As verbs, parlay and double up are synonyms defined as:

parlay (noun)	double up (noun)
a series of wagers in which the winnings from one wager are used as a stake for the subsequent wagers

parlay (verb)	double up (verb)
stake winnings from one bet on a subsequent wager	stake winnings from one bet on a subsequent wager
	bend over or curl up, usually with laughter or pain
	share a room or a bed designed for only one person