From WordNet (r) 3.0 (2006) [wn]:
propane
n 1: colorless gas found in natural gas and petroleum; used as a
fuel
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Propane \Pro"pane\, n. [Propyl + methane.] (Chem.)
A heavy gaseous hydrocarbon, C3H8, of the paraffin series,
occurring naturally dissolved in crude petroleum, and also
made artificially; -- called also propyl hydride.
[1913 Webster]