oy ‧ ster /ˈɔɪstə $ -ər/ BrE AmE noun [countable]
[ Date: 1300-1400 ; Language: Old French ; Origin: oistre , from Latin , from Greek ostreon ]
1 . a type of ↑ shellfish that can be eaten cooked or uncooked, and that produces a jewel called a ↑ pearl
2 . the world is your oyster used to tell someone that they can achieve whatever they want