(ˈ)vak|senik- noun
Etymology: Latin vacca cow + English -en (in octadecenoic ) + -ic
: a crystalline unsaturated acid C 6 H 13 CH . CH(CH 2 ) 9 COOH that is isomeric with elaidic acid and oleic acid and that is obtained especially in the trans form from beef fat and other animal fats and in the cis form from bacterial fats; 11-octadecenoic acid