1. A visual representation (of an object or scene or person or abstraction) produced on a surface; such as, a picture, image, or other representation.
2. Eastern Church, a representation of some sacred personage, as Christ or a saint or angel, painted usually on a wood surface and venerated itself as sacred.
3. A sign or representation that stands for its object by virtue of a resemblance or analogy to it.
4. An important and enduring symbol.
5. In semiotics, that stands for its object by virtue of a resemblance or analogy to it.
6. With computers, a sign, representation, or a picture on a computer screen that represents a specific file, directory, window, option, or program.

When an icon is clicked on, some action is performed; such as, opening a directory or aborting a file transfer.

The term originates from Alan Kay's theory for designing interfaces which was primarily based on the work of Jerome Bruner. Bruner's second developmental stage, iconic, uses a system of representation that depends on visual or other sensory organization and upon the use of summarising images.