Webster's Revised Unabridged Dictionary · 1913

Réseau

Réseau (rā`zō") , noun

[French]

(Astronomy) A network;
(a)
(Astronomy) 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.
(b)
(Astronomy) In lace, a ground or foundation of regular meshes, like network.

Also: Reseau