(n) the process whereby heavy molecules of naphtha or petroleum are broken down into hydrocarbons of lower molecular weight (especially in the oil-refining process)
(n) the process whereby hydrocarbon molecules of petroleum are broken down into kerosene and gasolene by the addition of hydrogen under high pressure in the presence of a catalyst
n. 1. the act of cracking something. Syn. -- fracture, crack. [ WordNet 1.5 ]
2. (Chem.) the process of making lower molecular weight hydrocarbons from heavier hydrocarbons in petroleum, by exposure to heat and catalysts. It is used to convert heavier alkanes into gasoline, or to improve the octane number of an alkane mixture. [ PJC ]