/ Dictionary / Index P pico-: Meaning and Definition of Find definitions for: pico- Pronunciation: [key] a combining form meaning “one trillionth” (10): picogram. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. picnic Pico della Mirandola Related Content Daily Word Quiz: mamba Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language