optical UK /ˈɒptɪkəl/US /ˈɑptɪkəl/adjective 5noun 1forms 3 adjective5 •Of or relating to sight; visual.Strabismus is an optical defect. •Of or relating to optics.Refraction is an optical effect. •Of or relating to visible light.Optical telescopes don't work when it is cloudy. •Incorporating light-sensitive devices.An optical switch opens the door automatically. •Designed to assist or enhance sightA microscope is an optical instrument. noun1 •Any special effect requiring laboratory work on the film.If you plan to output back to film, opticals and effects can be shot on film or generated by computer and then transferred to film. — 2006 formsopticals · more optical · most optical