sink, subside, or bulge downwards under weight or pressure or through lack of strength

she let her head sag lower and lower

the bed sagged in the middle

decline to a lower level, usually temporarily

exports are forging ahead while home sales sag

a downward curve or bulge in a structure caused by weakness or excessive weight or pressure

a sag in the middle necessitated a third set of wheels

a decline, especially a temporary one

spinach or another leafy vegetable