A tectonic plate is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere, that moves and interacts with other plates on the Earth’s surface. Tectonic plates are fundamental in understanding the mechanisms of plate tectonics, including continental drift, the formation of mountains, earthquakes, and volcanic activity.
Source Cox, A., & Hart, R. B. (1986). “Plate Tectonics: How It Works.” Blackwell Scientific Publications.