/ Dictionary / Index P planetoid: Meaning and Definition of Find definitions for: plan•et•oid Pronunciation: (plan'i-toid"), [key] — n. Astron. an asteroid. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: planetoid (Thesaurus) planet gear planetology Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language