Longitudinal hull bending where the middle is supported by a wave crest while the ends sag.
Regulatory detail & full definition
Hogging is the longitudinal bending condition in which a ship's hull is supported more amidships than at the ends — for example when a single large wave crest is amidships, or when heavy weights are concentrated at the fore and aft ends — so that the deck is put into tension and the bottom into compression. It is the opposite of sagging. Excessive hogging or sagging stresses the hull girder and is controlled through careful attention to the loading sequence and the longitudinal distribution of cargo and ballast, checked with the ship's approved loading computer against permissible still-water bending moments.