Intrasemiotic refers to a process belonging to or arising within the same semiotic system (sign system).
For comparison, intersemiotics examines the relationship between two different sign systems.
When one saxophonist responds to another during improvisation, it is an intrasemiotic exchange, as they both operate in the sign system of the music. However, if a dancer translates these musical improvisations into improvised movements, it is an intersemiotic exchange.