| 1. | Also called cross wires. fine wires or fibers, strands of spider web, or the like, crossing in a focal plane of an optical instrument to center a target or object or to define a line of sight. |
| 2. | marks for aiding in the positioning of overlaying images for correct registration in printing. Compare register (def. 11b). |
| cross hair or cross·hair (krôs'hâr', krŏs'-) n. Either of two fine strands of wire crossed in the focus of the eyepiece of an optical instrument and used as a calibration or sighting reference. |