The Collaborative International Dictionary of English v.0.48:

Trek \Trek\, n. [Written also treck.] [D. Cf. Track, n.]
   The act of trekking; a drawing or a traveling; a journey; a
   migration. [Chiefly South Africa]

         To the north a trek was projected, and some years later
         was nearly carried out, for the occupation of the
         Mashonaland.                             --James Bryce.

   Great Trek, the great emigration of Boers from Cape Colony
      which began in 1836, and resulted in the founding of the
      South African Republic and Orange Free State.
      [Webster 1913 Suppl.]