(*) A cloud which rolls out from the bottom of the column produced by a subsurface burst of a nuclear weapon. For underwater bursts the surge is, in effect, a cloud of liquid droplets which has the property of flowing almost as if it were a homogeneous fluid. For subsurface land bursts the surge is made up of small solid particles but still behaves like a fluid.
BASE SURGE
Meaning of BASE SURGE in English
DOD English dictionary of military terms. Английский словарь военных терминов DOD. 2012