The Collaborative International Dictionary of English v.0.48:

Sharecropper \Share"crop`per\, n.
   A farmer who rents a parcel of land from its owner and pays a
   portion of the crop as the rent.
   [PJC]

WordNet (r) 3.0 (2006):

sharecropper
    n 1: small farmers and tenants [syn: sharecropper, cropper,
         sharecrop farmer]