Real Dictionary

glissando in American English
(performed) with such an effect
a sliding effect achieved by sounding a series of adjacent tones in rapid succession, as by running a finger over the white keys of a piano
adjective: performed with a gliding effect by sliding one or more fingers rapidly over the keys of a piano or strings of a harp
noun: a glissando passage

glissando in British English
noun: a rapidly executed series of notes on the harp or piano, each note of which is discretely audible