Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


adjective plac·oid \ˈpla-ˌkȯid\

Definition of placoid

  1. :  of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs

Origin and Etymology of placoid

Greek plak-, plax flat surface

First Known Use: 1842

Seen and Heard

What made you want to look up placoid? Please tell us where you read or heard it (including the quote, if possible).