Tadpole pupil, also known as a keyhole pupil, refers to a narrow and elongated pupil shape that looks like a tadpole's tail. There are alternative ways to describe this peculiar pupil shape such as pinhole pupil, slit pupil, and cat's eye pupil. The pinhole pupil refers to a tiny and constricted pupil size, while the slit pupil is similar to a vertical elliptical shape. The cat's eye pupil, on the other hand, is a more complex shape that varies from a vertical slit to a crescent shape, commonly seen in animals such as cats and goats. These alternate ways of describing pupils help to convey the unique characteristics and changes in size or shape that can indicate different eye conditions.