A lens that has a picture angle of approximately 180 degrees or more. Read articles that include this term

An ultrawide-angle spherical lens that can capture up to a 180-degree field of view, or just about everything you can see in front of you. However, the image will be distorted, like looking through a [..]

A special lens that provides about a 180- degree field of view. In order to capture all 180 degrees in a single image, the picture will become distorted into an ellipse, like when looking through the peephole in a door.

An extreme wide angle lens. Most fisheye lenses cover a 180 degree angle of view, popular focal lengths include 6, 8 and 14mm. The 6mm and 8mm lenses produce a circular image on the film. (not full frame)

A lens that has a picture angle of approximately 180 degrees or more. Read articles that include this term

extreme wide-angle lens with an angle of view exceeding 100° and sometimes in excess of 180°. Depth of field is practically infinite and focusing is not required.

a lens with an extremely wide angle of view, as much as 180 degrees, and considerable barrel distortion (straight lines at the edges of a scene appear to curve around the center of the image)

A fisheye lens is a wide-angle lens that takes in a nearly 180-degree field of view.