Jamming range was an area in which one could be affected by a jamming signal.
In 2152, T'Pol reported that a shuttlepod she, Jonathan Archer, and Soval were travelling in was still within jamming range of the Andorians. (ENT: "Cease Fire")
In 2285, James T. Kirk ordered Spock that if he didn't hear from the landing party on Regula I, to fix the USS Enterprise as much as possible, head for the nearest starbase, and contact Starfleet Command the moment the starship was out of jamming range. (Star Trek II: The Wrath of Khan)