A portable device that stops a transporter from locking on to anyone within its range, planted by the Enterprise-E crew to protect the Ba'ku from abduction.
A transport inhibitor produces a field that prevents a transporter from locking on to people or objects nearby. Starfleet's portable version is a pole that can be driven into the ground, and several of them will cover a wide area.
The devices are central to the middle of Star Trek: Insurrection. Having learned that the Son'a and Admiral Dougherty mean to remove the Ba'ku from their planet by force, Picard and his officers lead the villagers out of their settlement towards caves in the hills and set inhibitors along the route so that they cannot simply be beamed aboard the Son'a ships.
The Son'a reply by sending flying drones that fire small tags into individual Ba'ku, which let a transporter seize them in spite of the field. Picard and Anij are among those taken in this way before the evacuation is over.