What is "trebles"

Usage examples of "trebles".

Dissdale himself, not only fully recovered but incoherent with joy as most of his doubles, trebles and accumulators had come up, patted Calder plumply on the shoulder and invited him over to "my place" for the weekend.

Let us assume that by the turn of the century the population trebles and energy requirements increase to ten kilowatts per person.