Thrust

Thrust was, as the Fifth Doctor explained, "mass in motion". (TV: Castrovalva) Thrust was generally produced by thrusters, such as those on a spacecraft. (TV: The Robots of Death et al) Explosions could also produce upwards thrust. (TV: The Dalek Invasion of Earth)

Rocket thrust was, according to Tegan Jovanka, "enormous". It was so large that it enabled escape from gravity, such as that of Event One. Deleting rooms in a TARDIS using the architectural reconfiguration system could also produce large amounts of thrust. (TV: Castrovalva)

According to the Thirteenth Doctor, positrons produced by the Tsuranga's particle accelerator interacted with the fuel materials to produce heat, which produced thrust. (TV: The Tsuranga Conundrum)

Other uses
A thrust could also refer to the use of a bladed weapon, such as a sword. (TV: The Masque of Mandragora, The Talons of Weng-Chiang)

Brigadier Alistair Gordon Lethbridge-Stewart once referred to an Auton incursion as a "diversionary thrust". (TV: Terror of the Autons)

The phrase 'thrust' was also a saying that meant to forcibly impose oneself on someone. (TV: The Chase)