crou ‧ pi ‧ er /ˈkruːpiə $ -ər/ BrE AmE noun [countable]
[ Date: 1700-1800 ; Language: French ; Origin: 'person who rides on the back end of a horse, person who stands behind a player and gives advice, croupier' , from Old French croupe 'back end of an animal' ]
someone whose job is to collect and pay out money where people play cards, ↑ roulette etc for money at a ↑ casino