I. ˌsōs-tə-ˈnü-(ˌ)tō, ˌsȯs- adjective or adverb
Etymology: Italian, from past participle of sostenere to sustain, from Latin sustinēre
Date: circa 1724
: sustained to or beyond the note's full value — used as a direction in music
II. noun
Date: 1757
: a movement or passage whose notes are markedly prolonged