NOUN (2)

1. any cell that has a specific receptor for an antigen or antibody or hormone or drug, or is the focus of contact by a virus or phagocyte or nerve fiber etc.;

2. an abnormal red blood cell with the appearance of a dark ring surrounding a dark center; associated with anemia;

WordNet (r) 3.0 (2006):

target cell
    n 1: any cell that has a specific receptor for an antigen or
         antibody or hormone or drug, or is the focus of contact by
         a virus or phagocyte or nerve fiber etc.
    2: an abnormal red blood cell with the appearance of a dark ring
       surrounding a dark center; associated with anemia