Rubato is a definition in musical interpretation.
Originally it means “robbed” time, i.e. stolen time.
Meaning that the interpreter, the performer,
can play “off” or “around” the metrum.
Rubato is defined during the Romantic Period.
When you’re listening to my PianoTweets,
you might notice that I use this very often,
almost in all pieces.
Very rarely I use a metronome.
For me Rubato is a way of “talking musically”,
using tempo variations as well as great volume dynamics.