sostenuto

In a manner that is sustained as long as or beyond a note’s full value. Used chiefly as a direction.

A sostenuto passage or movement.

In music, sustained; prolonged: sometimes merely the same as tenuto, and sometimes implying in addition a slight reduction of speed. Abbreviated sost.

Sustained; — applied to a movement or passage the sounds of which are to sustained to the utmost of the nominal value of the time; also, to a passage the tones of which are to be somewhat prolonged or protacted.

played in a sustained manner beyond the notes normal value

A note or passage marked to be sustained