The term 'DARK PATCH' can be described as a SHADOW or BLOT. A dark patch is an area of darkness, usually caused by a lack of light. It can also refer to a stain or discoloration on a surface. In the context of photography, a dark patch is an area of a photograph that appears darker than the rest of the image. In astronomy, a dark patch is a region of space that is particularly dark and devoid of stars.