glis·san·do / gliˈsändō/ • n. (pl. -di / -dē/ or -dos) Mus. a continuous slide upward or downward between two notes.

glissando (bastard It. from Fr. glisser, to slide).
1. (pf., harp, xylophone, vibraphone, etc.) The drawing of a finger down or up a series of adjacent notes.

2. (bowed instrs.) Passing all or part of the way from one note to another on the same str., in much the same way as above and with much the same effect—with the difference that the pitches passed through, instead of representing the fixed tones and semitones of a scale, are infinite in number. Tb. can also perform a satisfactory glissando.