Definitions:
consisting of three parts; threefold

three times as much or as many

three sporting victories or championships in the same season, event, etc.

a hit on the narrow ring enclosed by the two middle circles of a dartboard, scoring treble.

a type of bet in which three selections are made, with any winnings from the first being transferred to the second and then (if successful) to the third.

a thing that is three times as large as usual or is made up of three standard units or things.

a number or amount which is three times as large as a contrasting or usual number or amount

make or become three times as large or numerous

a high-pitched voice, especially a boy's singing voice

denoting a relatively high-pitched member of a family of similar instruments

the high-frequency output of a radio, or audio system, corresponding to the treble in music.