acra·nia or Acrania
n : congenital partial or total absence of the skull .
n pl, in some classifications : a division of the phylum or subkingdom Chordata comprising the hemichordates, tunicates, and lancelets and including all the chordates without true heads and anterior brains - compare VERTEBRATA .
Similar sounding terms: Ac·a·ri·na ac·a·rine
Published under license with Merriam-Webster, Incorporated. © 1997-2017.