The Collaborative International Dictionary of English v.0.48:

Vinyl \Vi"nyl\, n. [L. vinum wine + -yl.] (Chem.)
   The hypothetical radical C2H3, regarded as the
   characteristic residue of ethylene and that related series of
   unsaturated hydrocarbons with which the allyl compounds are
   homologous.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ethenyl \Eth"e*nyl\, n. [Ethene + -yl.] (Chem.)
   (a) A trivalent hydrocarbon radical, CH3.C.
   (b) A univalent hydrocarbon radical of the ethylene series,
       CH2:CH; -- called also vinyl. See Vinyl.
       [1913 Webster]

WordNet (r) 3.0 (2006):

vinyl
    n 1: a univalent chemical radical derived from ethylene [syn:
         vinyl, vinyl group, vinyl radical]
    2: shiny and tough and flexible plastic; used especially for
       floor coverings