A thruster pack, rocket pack or jet pack was a thruster unit that could be attached to an environmental suit in order to allow the person in the suit the ability of flight during a space walk. An EV suit with a thruster pack (a thruster suit) was normally used for missions on the outer hull of a spacecraft, or for missions that involved navigation that would be impossible or difficult for a shuttle, let alone a starship.
For example, in 2256, Commander Michael Burnham used a thruster pack to navigate a meteor field in order to take a closer look at an "object of unknown origin" that was detected by the sensors of the USS Shenzhou. (DIS: "The Vulcan Hello")
In 2259, Erica Ortegas asked Brad Boimler if there were any jetpacks in the future, despite the fact that they already had jetpacks in her own time period. She explained the reason she asked however, was because she wondered if they were smaller. (SNW: "Those Old Scientists")
An emergency evacuation thruster pack was a type of thruster pack designed to offer a single thruster burst. (Star Trek: The Motion Picture)