rallentando

adverb or adjective

ral·​len·​tan·​do ˌrä-lən-ˈtän-(ˌ)dō 

: ritardando

Word History

Etymology

Italian, literally, slowing down, verbal of rallentare to slow down again, from re- + allentare to slow down, from Late Latin, from Latin al- ad- + lentus slow, pliant — more at lithe

First Known Use

1786, in the meaning defined above