Definition of ascidian
: any of a class (Ascidiacea) of solitary or colonial sessile tunicates having an incurrent and excurrent siphon —called also sea squirt
Origin and Etymology of ascidian
New Latin Ascidia, group comprising tunicates, from Ascidium, genus name, from Greek askidion, diminutive of askos wineskin, bladder
First Known Use: 1823
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