plac·oid adjective \ˈpla-ˌkȯid\
: of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs
Origin of PLACOID
Greek plak-, plax
First Known Use: 1842
Seen & Heard
What made you want to look up placoid? Please tell us where you read or heard it (including the quote, if possible).