A network of fine lines, dots, cross hairs, or wires in the focal plane of the eyepiece of an optical instrument WordNet 3.0 & Open English WordNet

A reticle, or reticule also known as a graticule, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the screen of an oscilloscope, to provide measurement references during visual inspections. Wikipedia

Fine lines in the eyepiece of a sighting device Wikipedia Disambiguation

A nearly square or nearly rectangular region created by a graticule. Wiktionary

Region created by a graticule. Wiktionary (translation)

A grid, network, or crosshatch found in the eyepiece of various optical instruments to aid measurement or alignment. Wiktionary

A gridwork or lattice of lines set into the eyepiece of optical instruments. Wiktionary (translation)

A reticle; a grid in the eyepiece of an instrument. Wiktionary