The Collaborative International Dictionary of English v.0.48:

Phenacetin \Phe*nac"e*tin\, Phenacetine \Phe*nac"e*tine\, n.
   [Phenyl + acetic + -in.] (Pharm.)
   A white, crystalline compound, C10H13O2N, once used in
   medicine principally as an antipyretic. It is now seldom used
   because of serious side effects.

   Syn: N-(4-ethoxyphenyl)acetamide, p-acetophenetidide,
        p-ethoxyacetanilide, acetophenetidin,
        para-acetphenetidin, p-acetophenetide.
        [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

phenacetin
    n 1: a white crystalline compound used as an analgesic and also
         as an antipyretic [syn: acetophenetidin,
         acetphenetidin, phenacetin]