1 [data models] A spatial data model that defines space as an array of equally sized cells arranged in rows and columns, and composed of single or multiple bands. Each cell contains an attribute value and location coordinates. Unlike a vector structure, which stores coordinates explicitly, raster coordinates are contained in the ordering of the matrix. Groups of cells that share the same value represent the same type of geographic feature.
2 [ESRI software] In ArcGIS, an in-memory representation of a raster dataset. A raster may exist in memory as a subset of a raster dataset; it may have a different cell size than the raster dataset; or it may exist using a different transformation than the raster dataset.