carbon dioxiden. A colorless, odorless, incombustible gas, CO2, that is formed during respiration, combustion, and organic decomposition, is an essential component in photosynthesis, and is used in food refrigeration, carbonated beverages, inert atmospheres, fire extinguishers, and aerosols. Also called carbonic acid gas.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.carbon dioxide n (Elements & Compounds) a colourless odourless incombustible gas present in the atmosphere and formed during respiration, the decomposition and combustion of organic compounds, and in the reaction of acids with carbonates: used in carbonated drinks, fire extinguishers, and as dry ice for refrigeration. Formula: CO2. Also called: carbonic-acid gas Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014car?bon diox?ide n. a colorless, odorless, incombustible gas, CO2, present in the atmosphere and formed during respiration: used as dry ice and in carbonated beverages and fire extinguishers. [1870?75] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.carbon dioxide A colorless, odorless gas, CO2, that is present in the atmosphere and is formed when any fuel containing carbon is burned. It is breathed out of an animal’s lungs during respiration, produced by the decay of organic matter, and used by plants in photosynthesis. Carbon dioxide is also used in refrigeration, fire extinguishers, and carbonated drinks.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.carbon dioxideA gas in air. In the carbon cycle, plants make food with carbon dioxide, and breathing, burning, and decay return it to the air. See greenhouse gases.Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited