Definition of grists:
(n) :
Grain that is to be ground in a mill.
(v) :
(transitive) To grind in a mill.
(n) :
(ropemaking) A given size of rope, common grist being a rope three inches in circumference, with twenty yarns in each of the three strands.
(n) :
(colloquial, obsolete) Supply; provision.
(n) :
(obsolete) A group of bees.
(n) :
(figurative) Ellipsis of grist for the mill. [(idiomatic) Something that is useful or that creates a favorable opportunity.]