Sagging p. pr. & vb. n. : of Sag

Sagging n. : A bending or sinking between the ends of a thing, in consequence of its own, or an imposed, weight; an arching downward in the middle, as of a ship after straining. Cf. Hogging.

Example:
How do I fix loose, Sagging upholstery fabric on the ceiling of my car?

Taxonomy
fashion, ordinance, free encyclopedia, 11-23, dress codes, belts, disorderly conduct, jeans, underwear, Controversy, Town Council, search, the practice, waist, Riding, Origin, prohibition, prisoners.

Defination from the web:
Sagging is the practice of wearing pants or shorts below the waist so as to reveal some or all of the wearer's underwear, this is also referred to as Low-Riding in the UK.[1] ... Sagging is commonly reported in the media as having originated from the prohibition of belts for prisoners. ...