Real Dictionary

carbon monoxide
uncountable noun: Carbon monoxide is a poisonous gas that is produced especially by the engines of vehicles.

carbon monoxide in American English
a colorless, odorless, highly poisonous gas, CO, produced by the incomplete combustion of carbonaceous material: it burns with a pale-blue flame
noun: a colorless, odorless, poisonous gas, CO, that burns with a pale-blue flame, produced when carbon burns with insufficient air: used chiefly in organic synthesis, metallurgy, and in the preparation of metal carbonyls, as nickel carbonyl

carbon monoxide in Automotive Engineering
noun: Carbon monoxide is a poisonous gas that is produced especially by the engines of vehicles.

carbon monoxide in British English
noun: a colourless odourless poisonous flammable gas formed when carbon compounds burn in insufficient air and produced by the action of steam on hot carbon: used as a reducing agent in metallurgy and as a fuel. Formula: CO