Question

what do you mean by atmospheric pressure

Answer 1

Atmospheric pressure, sometimes also called barometric pressure, is the pressure exerted by the weight of air in the atmosphere of Earth (or that of another planet). In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point.

Answer 2

the force per unit area exerted against a surface by the weight of air above the surface is known as atmospheric pressure