Basophilic is a technical term used by histologists. It describes the microscopic appearance of cells and tissues, as seen down the microscope, after a histological section has been stained with a basic dye. The most common such dye is haematoxylin.
Basophilic describes the appearance of structures seen in histological sections which take up basic dyes.
The structures usually stained are those that contain nucleic acid such as the cell nucleus and ribosomes.