Signifier

Merriam-Webster Online defines 'Signifier' as:

Main Entry: sig·ni·fi·er
Pronunciation: \ˈsig-nə-ˌfī(-ə)r\
Function: noun
Date: 1532

1 : one that signifies
2 : a symbol, sound, or image (as a word) that represents an underlying concept or meaning — compare signified