"Weightless" refers to the condition experienced when there is no net gravitational force acting on an object or person. This sensation is commonly felt in space, where astronauts experience microgravity, allowing them to float freely. The term can also apply to specific environments, such as free-fall or during certain phases of flight. In scientific terms, weightlessness occurs when the force of gravity is countered by other forces, such as centrifugal force during orbital motion. This phenomenon is crucial for understanding the effects of microgravity on the human body and various physical processes, making it a significant area of study in space exploration.