oyster mushroom means: This mushroom is a smooth-capped, fan-shaped one with mild oyster-like flavors. You can find them fresh or dried in most supermarkets, as well as many oriental markets. (in Cooking Dictionary)

What else does oyster mushroom mean?

It is a fan-shaped wild mushroom that has a grayish cap and grows in small clusters along the sides of trees. The mushrooms are soft and grayish-colored, with a slightly soft texture. They have a subtle taste. These mushrooms are also grown in America, which makes them easily available on markets and relatively affordable. (in Cooking Dictionary)

One of many edible mushrooms in the genus Pleurotus, A soft grayish, flavourful cap. (in Merlin Dictionary)