butyl

from WordNet (r) 3.0 (2006)

butyl
    n 1: a hydrocarbon radical (C4H9)

from The Collaborative International Dictionary of English v.0.48

Butyl \Bu"tyl\, n. [L. butyrum butter + -yl. See {Butter}.]
   (Chem.)
   A compound radical, regarded as butane, less one atom of
   hydrogen.
   [1913 Webster]