The free, uninsulated wire (except at supports) extended several hundred feet through the air.
The interior sphere was insulated, the external one uninsulated.
Straight ahead they went now, bending low, dodging elbows of big gas mains, on the alert for uninsulated electric wires.
Thus the train, wherever it stands, bridges a gap separating the insulated from the uninsulated section.
1530s, "make into an island," from Latin insulatus, from insula (see insular). Sense of "cause a person or thing to be detached from surroundings" is from 1785. Electrical/chemical sense of "block from electricity or heat" is from 1742. Related: Insulated; insulating.