An optical instrument with a lens for each eye, used for viewing distant objects
(In singular and plural) = prism binocular.
(In singular and plural) binoculars containing two pairs of triangular prisms, introduced so as to shorten the instrument and improve the stereoscopic effect.
A pair of binoculars using two porro prisms at right angles, resulting in a conventional instrument with objective lenses that are further apart than the eyepieces
A pair of binoculars using two roof prisms, resulting in an instrument with parallel sides and objective lenses that are the same distance apart as the eyepieces