D defs.my
Entry 2 senses Webster, 1913

Acrania

· A·cra·ni·a · IPA /(ˌ)eɪˈkreɪ.ni.ə/
01 n. Partial or total absence of the skull.
  1. 1.
    Partial or total absence of the skull.(Physiol.)
  2. 2.
    The lowest group of Vertebrata, including the amphioxus, in which no skull exists.(Zool.)