The Collaborative International Dictionary of English v.0.48:

Nabk \Nabk\ (n[a^]bk), n. [Ar. nabiqa, nibqa.] (Bot.)
   The edible berries of the Zizyphys Lotus, a tree of
   Northern Africa, and Southwestern Europe. [Written also
   nubk.] See Lotus
   (b), and Sadr.
       [1913 Webster]