A line or wire from the mast to the bow or stern of a ship, for support of the mast (fore, back, running, and triadic stays). A vessel is said to be in stays when she is going through the operation of tacking. To stay is to tack. Strictly, when a ship is head to wind. Probably derived from the fact that a square rigged ship "stays" a long time before her bead pays off, and she is than "in stays."