allargando
adjective or adverb
al·lar·gan·do ˌä-lär-ˈgän-(ˌ)dō 
: becoming gradually slower and more stately —used as a direction in music
Word History
Etymology
Italian, widening, verbal of allargare to widen, from al- (from Latin ad-) + largare to widen
First Known Use
1877, in the meaning defined above