(originally United States) A bet or series of bets where the stake and winnings are cumulatively carried forward; an accumulator.

To carry forward the stake and winnings from a bet on to a subsequent wager or series of wagers.

(by extension) To increase (an asset, money, etc.) by gambling or investing in a daring manner.

“Shall we parlay the value of our products?”

(by extension, generally) To convert (a situation, thing, etc.) into something better.

To have a discussion, especially one between enemies.