Definition from Wiktionary, the free dictionary
emoticon (plural emoticons)
- A graphical representation, either in the form of an image or made up of ASCII characters, of a particular emotion of the writer.
respresentation of an emotion of the writer
Usage notes 
In contexts with image-based emoticons, emoticon often refers specifically to image-based glyphs, while smiley refers to text-based ones.
See also 
emoticon m (invariable)