1. The amount of positive pressure created in an intake system above normal atmospheric pressure by a turbocharger or supercharger. Normal atmospheric pressure is 14.7 psi. A blower providing 10 psi boost increases the pressure to 24.7 psi. Boost is sometimes measured in atmospheres where one atmosphere equals 14.7 psi. Thus 24.7 psi is about 1.7 atmospheres. 2. The action of jump starting one battery from another.