Wiktionary
electrical tape
n. A poorly conductive plastic tape used to insulate electrical wires.
Wikipedia
Electrical tape
Electrical tape (or insulating tape) is a type of pressure-sensitive tape used to insulate electrical wires and other materials that conduct electricity. It can be made of many plastics, but vinyl is most popular, as it stretches well and gives an effective and long lasting insulation. Electrical tape for class H insulation is made of fiberglass cloth.