What is medusa in biology

a medusa is a form of cnidarian in which the body is shortened on its principal axis and broadened, sometimes greatly, in contrast with the hydroid or polyp. In biology, a medusa (plural: medusae) is a form of cnidarian in which the body is shaped like an umbrella. The other main body-form is the polyp. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below.

Is a form of cnidarian in which the body is shaped like an umbrella

Explanation:

The other main body-form is the polyp. Medusae vary from bell-shaped to the shape of a thin risk, scarcely convex above and only slightly concave below