Other forms: swapped, swapping, swaps
To swap is to give one thing and get another back. Swap seats, swap places, a straight swap.
It is informal; exchange is the formal equivalent. Swap with somebody, swap something for something. As a noun, a swap is the exchange itself: do a swap. In finance, a swap is a contract exchanging one stream of payments for another, which is a serious technical term. Note swap shop and swap meet; and that swop is an accepted British variant spelling that has almost died out.
1verbswapTo give one thing and get another back.
“They swapped houses for about a fortnight.”
2nounexchangeAn exchange of one thing for another.
“It was a straight swap and nobody paid anything.”
swap is an exchange.
Also accepted in games: exchange, trade
Middle English swappen meant to strike, and the modern sense probably comes from striking hands to seal a bargain — the handshake that closed a deal in a market. The blow became the exchange.
Middle English
swappen
English, today
swap
From Middle English swappen. From Middle English swappen (“to swap”), originally meaning "to hurl" or "to strike", the word alludes to striking hands together when making an exchange; probably from Old English swappian, a secondary form of Old English swāpan (“to swoop”). Cognate with German schwappen (“to slosh, slop”). Compare also Middle English swippen (“to strike, hit”), from Old English swipian (“to scourge, strike, beat, lash”), Old Norse svipa (“to swoop, flash, whip, look after, look around”). More at swipe.
Etymology from Wiktionary, CC BY-SA