1) Becoming progressively slower 2) Decreasing 3) Decelerating 4) Gradually decreasing in tempo 5) Italian musical term 6) Italian tempo term 7) Musical term to an Italian 8) Musical term in Rome 9) Ritardando 10) Ritenuto 11) Slowing down 1) Ritardando 2) Ritenuto 
• (a.) Slackening; -- a direction to perform a passage with a gradual decrease in time and force; ritardando.
Ral`len·tan'do (räl`lĕn*tän'do) adjective [ Italian ] (Mus.) Slackening; -- a direction to perform a passage with a gradual decrease in time and force; ritardando. 
rallentando 
In music rallentando is a direction to perform a passage with a gradual decrease in time and force.
Rallentando means gradually becoming slower. It also is abbreviated as rall.
[adj] - gradually decreasing in tempo 2. [adv] - (music) slowing down
ritardando adjective gradually decreasing in tempo
gradually getting slower
a musical direction term meaning getting slower.
gradually slow down