réseau

Century Dictionary and Cyclopedia

1. n. In lace-making, the ground when composed of regular uniform meshes, whether of one shape only or of two or more shapes alternating.
2. n. A network of small squares formed by two sets of fine, parallel, equidistant lines, some millimeters apart, crossing each other at right angles, accurately ruled upon a glass plate. This is interposed in a photographic telescope immediately in front of the sensitive plate, so that its lines are impressed upon the negative and furnish reference-points from which the positions of star-images can be measured. Its use is not without some drawbacks, but presents some great advantages, and, on the whole, is favorable to accuracy.
3. n. A diffraction grating. See grating, 2 .
4. n. a sort of network of regions alternately distinct and blurred, covering the sun's surface, according to the earlier photographs of Janssen made with wet plates. Later results, however, seem to indicate that the phenomenon was not solar but purely photographic.

GNU Webster's 1913

1. n. (Astron.) A system of lines forming small squares of standard size, which is photographed, by a separate exposure, on the same plate with star images to facilitate measurements, detect changes of the film, etc.
2. n. In lace, a ground or foundation of regular meshes, like network.

WordNet 3.0

1. n. a network of fine lines used by astronomers as a reference for measurements on star photographs
2. n. a net or mesh foundation for lace