Definition of sprags:
(n) :
A billet of wood; a piece of timber, a similar solid object or constructed unit used as a prop.
(v) :
(transitive) To prop or sustain with a sprag.
(v) :
(transitive) To check the motion of, as a carriage on a steep slope, by putting a sprag between the spokes of the wheel.
(adj) :
Alternative form of sprack. [(UK, dialectal) lively, full of energy]