A pattern interrupter was a device that blocked transporter function.
The prison on Radvek V was protected by a pattern interrupter that prevented transporter and communicator usage within a half-kilometer radius. The limit of its operation was delineated by boundary markers. (DIS: "The Examples")
Booker's ship was equipped with a pattern interrupter. It was disabled in 3190 when the ship was rammed by a shuttle from USS Discovery. (DIS: "Coming Home")