A shallow depression or hollow in a bone or organ. The surgeon noted the presence of a fossa in the patient's skull during the operation.
A carnivorous mammal native to Madagascar, resembling a small cougar. The fossa is the largest predator on the island of Madagascar.
In planetary geology, a long, narrow, shallow depression or trench on the surface of a planet or moon. Images from the Mars orbiter revealed a newly discovered fossa stretching hundreds of kilometers across the plain.