The Collaborative International Dictionary of English v.0.48:

Soapsuds \Soap"suds`\, n. pl.
   Suds made with soap.
   [1913 Webster]

WordNet (r) 3.0 (2006):

soapsuds
    n 1: the froth produced by soaps or detergents [syn: soapsuds,
         suds, lather]