treble
verb [ I or T ]
uk/ˈtrebl/ usto increase to three times the size or amount, or to make something do this:
profits/sales/shares treble In its first six months, Camelot's profits trebled.
a cost/price trebles The price of property has almost trebled in the last two years.
They invested $2m in trebling capacity at their processing plant last year.
See also
triple adjective