The Collaborative International Dictionary of English v.0.48:

Agistment \A*gist"ment\, n. [OF. agistement. See Agist.] (Law)
   (a) Formerly, the taking and feeding of other men's cattle in
       the king's forests.
   (b) The taking in by any one of other men's cattle to graze
       at a certain rate. --Mozley & W.
   (c) The price paid for such feeding.
   (d) A charge or rate against lands; as, an agistment of sea
       banks, i. e., charge for banks or dikes.
       [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

AGISTMENT, contracts. The taking of another person's cattle into one's own
ground to be fed, for a consideration to be paid by the owner. The person
who receives the cattle is called an agister.

     2. An agister is bound to ordinary diligence, and of course is
responsible for loses by ordinary negligence; but he does not insure the
safety of the cattle agisted. Jones, Bailm. 91; I Bell's Com. 458; Holt's N.
P. Rep. 547; Story, Bail. Sec. 443; Bac. Ab. Tythes, C l.