A cut-in is a shot that shows material present in a scene in greater detail, usually using a close-up shot.
Cut-in isolates and emphasizes an element of the mise-en-scène for dramatic or informational value. Each progressive movement through the shot sequence, from long shot to close-up, constitutes a form of cut-in. A cut-in made from a long shot to a big close-up can have a startling effect on the viewer because of this immediate magnification. This technique is frequently an editing method of suspense films.
Related, there is the insert shot, which is a shot containing visual detail that is inserted into a scene for informational purposes or to provide dramatic emphasis. A close-up view of printed material in a book, intercut as a character reads, is a type of informational point-of-view insert. The intercutting of a close-up view of a gun resting on a desk within a room where a violent argument is occurring constitutes a type of dramatic insert. Detail shot is another term for insert short.