ral·len·tan·do 
(răl′ən-tăndō, räl′lĕn-tändō) Music
(răl′ən-tăndō, räl′lĕn-tändō) Music adv. & adj.
Gradually slackening in tempo; ritardando. Used chiefly as a direction.
n. pl. ral·len·tan·dos
A rallentando passage or movement.
[Italian, present participle of rallentare, to slow down : re-, intensive pref. (from Latin; see RE-) + allentare, to slow down (from Late Latin allentāre : Latin ad-, ad- + Latin lentus, slow).]