Thrust force is defined by Newton's third law, where expelling mass, such as exhaust from a rocket nozzle, generates an equal and opposite force that propels the vehicle forward. It is essential for overcoming drag, which is the backward force that slows down motion, while lift is the crosswise force that keeps an aircraft airborne. Understanding thrust can be enhanced by observing jet engines in action during takeoff. Calculating thrust involves specific equations, and while Wikipedia can be a useful resource for formulas, users should verify the information for accuracy. Overall, thrust is a critical component of propulsion in both aerospace and aerodynamics.