pronunc at exchange I+ə(r) noun
Etymology: Middle English eschaungeour, from Anglo-French eschaungeor, from Old French eschangier to exchange + -eor -or
1. : one that exchanges
2. : money changer , banker ; especially : one formerly appointed in England to exchange plate and bullion for coin under royal authority
3. : an agent or apparatus for carrying out exchange reactions or processes: as
a. : ion exchanger
b. : heat exchanger