1. [adj]  of or relating to or involving light or optics; "optical supplies"
2. [adj]  relating to or using sight; "ocular inspection"; "an optical illusion"; "visual powers"; "visual navigation"
3. [adj]  of or relating to or resembling the eye; "ocular muscles"; "an ocular organ"; "ocular diseases"; "the optic (or optical) axis of the eye"; "an ocular spot is a pigmented organ or part believed to be sensitive to light"

OPTICAL is a 7 letter word that starts with O.