/ Dictionary / Index D deci-: Meaning and Definition of Find definitions for: deci- Pronunciation: [key] a combining form meaning “tenth,” used in words denoting units of the metric system (deciliter); on this model, extended to other systems (decibel). Cf. deca-. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. dechlorinate decibar Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language