amyl(n = noun.substance) - a hydrocarbon radical that occurs in many organic compounds;
is a kind of chemical group, group, radical

   A univalent hydrocarbon radical, C5H11, of the paraffine series found in amyl alcohol or fusel oil, etc. [1913 Webster]

amyl, n. (used attrib.) Chem. the monovalent group C5H11-, derived from pentane. Also called PENTYL.

Etymology:
L amylum starch, from which oil containing it was distilled

amyl alcohol, amyl nitrate, amyl nitrite