Definify.com
Webster 1913 Edition
Medusa
‖
Me-du′sa
,Noun.
 [L., fr. Gr. [GREEK].] 
1. 
(Class. Myth.) 
The Gorgon; or one of the Gorgons whose hair was changed into serpents, after which all who looked upon her were turned into stone. 
2. 
[pl. 
Medusae
.] (Zool.) 
Any free swimming acaleph; a jellyfish. 
☞ The larger medusae belong to the Discophora, and are sometimes called 
covered-eyed medusae
; others, known as naked-eyed medusae
, belong to the Hydroidea, and are usually developed by budding from hydroids. See Discophora
, Hydroidea
, and Hydromedusa
.