squa·lene 
(skw
āl
ēn
′)
n. An unsaturated aliphatic hydrocarbon, C30H50, that is the biosynthetic acyclic precursor to tetracyclic steroids such as cholesterol. It is widely found in animals, plants, and fungi and is present in high concentrations in shark liver oil and human sebum.
[New Latin Squalus, shark genus (from its occurrence in the liver oil of sharks) (from Latin squalus, a sea fish) + -ENE.]