Thill (?), n. [OE. thille, AS. �ille a board, plank, beam, thill; akin to �el a plank, D. deel a plank, floor, G. diele, OHG. dili, dilla, Icel. �ilja a plank, planking, a thwart, �ili a wainscot, plank; cf. Skr. tala a level surface. √236. Cf. Fill a thill, Deal a plank.] 1. One of the two long pieces of wood, extending before a vehicle, between which a horse is hitched; a shaft.
2. (Mining) The floor of a coal mine. Raymond.
Thill coupling, a device for connecting the thill of a vehicle to the axle.