High-tension wires carry a very strong electric current, the kind that travels long distances from power stations. Tension here is an old engineering word for the electrical pressure in a line — close to what people now call voltage — not the feeling of being stressed. You see it on warning signs, in news after storms when lines fall, and in technical talk. Many people now say high-voltage instead; high-tension is a bit older and still common for the wires themselves, especially high-tension cables or high-tension power lines. Do not touch them. English also uses tension for a tight, nervous atmosphere, and some writers say a high-tension match that way — but this entry is the electrical one.