A booster rocket was a component used in levitation boots to propel one or more up in the air quickly.

In 2287, James T. Kirk ordered Spock to activate the booster rockets on his jet boots, so he, Spock and Dr. Leonard McCoy could escape from Sybok's followers and a brainwashed Hikaru Sulu in the USS Enterprise-A's turboshaft. (Star Trek V: The Final Frontier)