Is an lion an amphibian

No, lions don't live in the water , they stay on land.

An amphibious organism ; (Amphibia) of cold-blooded vertebrates (as frogs, toads, or salamanders) intermediate in many characters between fishes and reptiles and having gilled aquatic larvae and air-breathing adults. A Lion is a mammal, (Mammalia) of warmblooded higher vertebrates (as placentals, marsupials, or monotones) that nourish their young with milk secreted by mammary glands, have the skin usually more or less covered with hair, and include humans.