A term used when printing a 3D object with a slicer. The hatching is the distance between two parallele and juxtaposed paths of the printing head (extrusion, inkjet) or two paths of the laser (photo-lithograhy). Takes effect in the XY plane. The associated Z term is the slicing.
Big hatchings can lead to rough surface and less dense structure. It can even lead to parallele lines not touching themselve and loss of the structure. Small hatchings lead to smooth surface by overlapping of juxtaposing lines.