1. (in physics) Symbol P. The rate at which work is done or energy is transferred. In SI units it is measured in watts (joules per second). See also horsepower.
2. (in mathematics) The number of times a quantity is multiplied; e.g. x5 is the fifth power of x. A power series is one in which the power of the variable increases with each term, e.g. a0 + a1x + a2x2 + a3x3 + … + anxn.