A cluster glissando is a short accented glissando.
The general production of a cluster glissando is the same as for a Glissando.
A cluster glissando, however, is executed faster and is more accented than a glissando. It is more similar to a fast arpeggio than to a glissando. It can consist of only a couple of notes or cover a large span of notes. The cluster glissando can be produced upwards or downwards or even simultaneously upwards and downwards (X-cluster glissando).
Cluster glissando/X-cluster glissando.
A cluster glissando sounds like a glissando played so fast that the single notes are not distinguishable. The sound is perceived as a cluster rather than a glissando.
A cluster glissando is notated with a group of notes, an arrow between two notes or a cluster. The notes are combined with an arpeggio sign and the abbreviation gliss. The arrow-head shows the direction of the cluster glissando.