Definition of Medusa's head in US English:

Medusa's head

(also Medusa-head)

noun

  • 1Zoology. Any of various echinoderms with multiply-branched arms, especially basket stars such as Gorgonocephalus; (formerly also) †the crinoid Cenocrinus asteria (formerly known as Pentacrinus caputmedusae) (obsolete).

  • 2A South African spurge, Euphorbia caput-medusae, with many long intertwining stems.

Origin

Mid 16th century (in an earlier sense). From the genitive of Medusa + head.