Rubato – The temporary abandonment of strict tempo, allowing the performer to be more flexible with their pace
To remember what rubato means, use the following mnemonic:
He rues the day he threw the baton over (rubato) to him, because the orchestra then kept going away from the strict tempo.
Rubato literally means "robbed time", where rhythms are placed freely for expressive effect. Another way of thinking of rubato is a more flexible tempo. A certain amount of freedom is allowed to express emotion.