“+ noun
Etymology: methyl + naphthalene
: either of two isomeric hydrocarbons C 10 H 7 CH 3 occurring in coal tar and petroleum:
a. : an oily liquid used as a reference fuel in determining the cetane number — called also alpha- or 1-methylnaphthalene
b. : a crystalline solid used chiefly in organic synthesis (as of menadione) — called also beta- or 2-methylnaphthalene