Rasterize, also spelled rasterise, is the process of converting a vector image (a mathematically defined image of points and curves) to a raster image (a picture composed of discrete pixels). More plainly, taking scene geometry and converting it to pixels for display on a screen or for printing purposes.
Rasterization is commonly used in real-time 3D graphics processing to convert images quickly for display on a computer monitor. It may also be used to edit still media. For instance, a vector image saved in the EPS format can be rasterized using a raster image editor like Adobe Photoshop or GIMP, and saved as a JPEG file.