Meteorol. 1. a U.S. National Weather Service advisory of sustained winds, over coastal and inland waters, with speeds of 20–33 knots (23–38 mph, 10–17 m/sec). Regional NWS offices have discretion over the choice of the lower limit.
2. an advisory of potentially dangerous sea surface conditions, as high swells, that are not directly related to local winds, accompanied by the reason for the advisory. Cf. advisory (def. 4).