Webster's Revised Unabridged Dictionary · 1913

Sag

Sag (sag) , intransitive verb

[Akin to Swedish sacka to settle, sink down, LG. sacken, Dutch zakken. Compare Sink, v. i.]

1.
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.
2.
Figuratively: 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. [Rare]
The mind I sway by, and the heart I bear, Shall never sag with doubt nor shake with fear. — Shakespeare
3.
To loiter in walking; to idle along; to drag or droop heavily.
Collocations (1)
To sag to leeward (Nautical) , to make much leeway by reason of the wind, sea, or current; to drift to leeward; -- said of a vessel. — Totten

Sag , transitive verb

To cause to bend or give way; to load.

Sag , noun

State of sinking or bending; sagging.