Rallentando
/ˌrælənˈtændəʊ/
Definition 1 of 1
Pro Tip 1/3Music-Specific Term
Use 'rallentando' when talking about the speed of music, not for other slow-downs. 
He signaled for a rallentando at the song's climax.
Pro Tip 2/3Creates Tension
'Rallentando' often adds suspense or emotional intensity to a piece of music. 
The rallentando before the final note added a haunting quality.
Pro Tip 3/3Concert Context
In orchestral music, 'rallentando' is a cue for musicians to slow the tempo together. 
The conductor's baton gestured for a rallentando as the concerto neared its end.