[op.ti.cal] adj (1570) 1: of or relating to the science of optics
2. a: of or relating to vision: visual b: visible 1 "~ wavelength" c: of, relating to, or being objects that emit light in the visible range of frequencies "an ~ galaxy" d: using the properties of light to aid vision "an ~ instrument" 3 a: of, relating to, or utilizing light esp. instead of other forms of energy "~ microscopy" b: involving the use of light-sensitive devices to acquire information for a computer "~ character recognition"
4: of or relating to optical art -- op.ti.cal.ly adv