The unit used by meteorologists to measure the pressure of atmosphere is bar (millibar).

Explanation

**Step-by-Step Solution:**

1. **Understanding Pressure in Liquids and Gases**:
- Both liquids and gases exert pressure in all directions. This is a fundamental property of fluids.

2. **Pressure on Container Walls**:
- When a liquid or gas is contained within a vessel (like a bottle or a cylinder), it applies pressure on the walls of that container. This is due to the movement of particles in the fluid, which collide with the walls.

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