tremolo
In the case of the ukulele, tremolo is the rapid repetition of the same sound on the same string, using two or three fingers of the fret hand in alternate picking or a dedillo. Tremolo belongs to the musical embellishments. Like the Vibrato it produces an acoustic beat. But cf. trill. As the sustain of an ukulele is rather short, tremolo can be used to lengthen the duration of a note.
Tremoli are a classic field of application for the pick.