oc ‧ tane /ˈɒkteɪn $ ˈɑːk-/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Language: Latin ; Origin: octo 'eight' ; because it has eight carbon atoms ]
a type of ↑ hydrocarbon that is in ↑ fuel and is used as a measure of its quality:
low octane petrol
high octane fuel