To sink, in the middle, by its weight or under applied
pressure, below a horizontal line or plane; as, a line or cable
supported by its ends sags, though tightly drawn; the floor of a room
sags; hence, to lean, give way, or settle from a vertical position; as,
a building may sag one way or another; a door sags on its hinges.

Fig.: To lose firmness or elasticity; to sink; to droop; to
flag; to bend; to yield, as the mind or spirits, under the pressure of
care, trouble, doubt, or the like; to be unsettled or unbalanced.

To loiter in walking; to idle along; to drag or droop
heavily.

To cause to bend or give way; to load.