To Sag

1. To sink, in the middle, by its weight or under applied pressure, below a horizontal line or plane.
2. (by extension) To lean, give way, or settle from a vertical position.
3. (figuratively) To lose firmness, elasticity, vigor, or a thriving state; 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.
4. To loiter in walking; to idle along; to drag or droop heavily.
5. (transitive) To cause to bend or give way; to load.
6. (informal) To wear one's trousers so that their top is well below the waist.
7. (informal, Canada) To pull down someone else's pants.