Construction of equipment or system installed outdoors without a cover which protects it from the effects of wind and rain.
There are the following types of water-proofing:
Water-proof types: Drip-proof, Rain-proof, Splash-proof, Water injection-proof, Water-proof, Water immersion-proof, Water dipping-proof and Humidity-proof.
Note: For the definition of each water-proof term, see JIS C0920.

Wave Length

Distance a wave travels in one cycle.

Whirling

Turning motion of the shaft center line.

Withstand Voltage (Electric Strength)

Voltage which the insulation of electrical equipment can withstand over a fixed period.
Example: 1 minute at a withstand voltage of 1000VAC (between each power terminal and the grounding terminal)