The Collaborative International Dictionary of English v.0.48:

Proletariat \Prol`e*ta"ri*at\, n. [F.]
   The indigent class in the State; the body of proletarians.
   [1913 Webster]

WordNet (r) 3.0 (2006):

proletariat
    n 1: a social class comprising those who do manual labor or work
         for wages; "there is a shortage of skilled labor in this
         field" [syn: labor, labour, working class,
         proletariat]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "proletariat":
   bourgeoisie, common people, common run, common sort, commonage,
   commonality, commonalty, commoners, commons, laborers,
   linendrapers, lower classes, lower middle class, lower orders,
   lumpen proletariat, middle class, middle orders, ordinary people,
   peasantry, plain folks, plain people, rank and file, shopkeepers,
   small tradesmen, the lower cut, the other half, the third estate,
   toilers, toiling class, upper middle class, vulgus, working class,
   working people