/ Dictionary / Index P placoid: Meaning and Definition of Find definitions for: plac•oid Pronunciation: (plak'oid), [key] — adj. platelike, as the scales or dermal investments of sharks. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: placoid (Thesaurus) placoderm plafond Related Content Daily Word Quiz: serendipity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language