What does "medusa" mean?

Medusa: [pl. Medusae (.] (Zoöl.) Any free swimming acaleph; a jellyfish. Note: The larger medusæ belong to the Discophora, and are sometimes called covered-eyed medusæ; others, known as naked-eyed medusæ, belong to the Hydroidea, and are usually developed by budding from hidroids. See Discophora, Hydroidea, and Hydromedusa. Medusa bud (Zoöl.), one of the buds of a hydroid, destined to develop into a gonophore or medusa. See Athecata, and Gonotheca. -- Medusa's head. (a) (Zoöl.) An astrophyton. (b) (Astron.) A cluster of stars in the constellation Perseus. It contains the bright star Algol.