Excessive pressure or urging. Source: Websters Dictionary Overpressure (or blast overpressure) is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion, and the resulting overpressure receives particular attention when measuring the effects of nuclear weapons or thermobaric bombs. (An OSH glossary used in safety and health at work which is, adopted by ILO