1. Chiefly medicine, referring to how lymph or life fluid is pushed through the vessel’s surrounding tissue: When Timmy fell down and hurt his knee badly, the blood extravasated into the area around the wound causing it to bruise and turn black and blue!
2. In geology, descriptive of the gushing forth of molten lava from an erupting volcano: The students in the geology class at school learned about how houses and villages in mountainous areas can be destroyed when volcanos extravasate and emit hot gas, rocks, ash, and melted rock through its vent at the top and into the air.