Dictionary.net

• 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

2006 - WordNet 3.0
By Princeton University

• 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

2011 - English Dictionary Database
By DataStellar Co., Ltd