Webster's Revised Unabridged Dictionary · 1913

Tasto

Tasto (tas"to) , noun

[Italian]

(Music) A key or thing touched to produce a tone.
Collocations (1)
Tasto solo , single touch; -- in old music, a direction denoting that the notes in the bass over or under which it is written should be performed alone, or with no other chords than unisons and octaves.