1. The grid of intersecting lines on which a map is drawn (for example, a grid of latitude and longitude).
2. A grid or pattern in the eyepiece of an optical instrument (such as a gunsight); a reticle.
3. A scale on transparent material on an instrument, for the location and measurement of objects (for example, the grid on an oscilloscope).
Etymology: Early 1900s. From Latin craticula, gridiron or latticework.