IP stands for Ingress Protection
IP (Ingress Protection) numbers are used to specify the environmental protection afforded by enclosures. These ratings refer to specific tests and are composed of two numbers. The first number is the protection from solid objects, and the second is the protection from liquids. To see work out the protection that a particular number represents, see the summary below.
FIRST NUMBER - Protection against solid objects
0. No protection
1. Protected against solid objects up to 50mm e.g. accidental touch by hands
2. Protected against solid objects up to 12mm e.g. fingers
3. Protected against solid objects up to 2.5mm (tools and wires)
4. Protected against solid objects up to 1mm (small tools and wires)
5. Protected against dust, limited ingress (no harmful deposit)
6. Totally protected against dust
SECOND NUMBER - Protection against liquids
0. No protection
1. Protection against vertically falling drops of water e.g. condensation
2. Protection against direct sprays of water up to 15 degrees from vertical
3. Protection against direct sprays of water up to 60 degrees from vertical
4. Protection against water sprayed from all directions - limited ingress permitted
5. Protected against low-pressure jets of water from all directions - limited ingress permitted
6. Protected against low pressure jets of water (such as use on ship decks) - limited ingress permitted
7. Protected against the effect of immersion between 15cm and 1m
8. Protected against long periods of immersion under pressure
Also refer to attached PDF document.