| ̷ ̷ ̷ ̷+ noun
Etymology: International Scientific Vocabulary is- + octane
: an octane of branched-chain structure or a mixture of such octanes: as
a. : the flammable liquid hydrocarbon (CH 3 ) 2 CH(CH 2 ) 4 CH 3 in whose molecule there is branching only at one end of the chain; 2-methyl-heptane
b. : a flammable liquid hydrocarbon (CH 3 ) 2 CHCH 2 C(CH 3 ) 3 made usually by hydrogenation of diisobutylene and used especially as a standard in rating motor fuels by their octane number; 2,2,4-trimethyl-pentane — not used technically
c. : hydrocodimer — used chiefly commercially