/ Dictionary / Index A acapnia: Meaning and Definition of Find definitions for: a•cap•ni•a Pronunciation: (u-kap'nē-u, ā-kap'-), [key] — n. Med. a deficiency of carbon dioxide in the blood and tissues. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: acapnia (Thesaurus) acanthus family a cappella Related Content Daily Word Quiz: knead Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language