Wiktionary
n. (context Internet English) A visual depiction of user-generated tags, typically used to describe the content of web sites and having the more significant tags shown in correspondingly larger text or a bolder font
Wikipedia
[[ 2.0 Map.svg|thumb|A tag
cloud with terms related to Web 2.0]]
A tag cloud (word cloud, or weighted list in visual design) is a visual representation of text data, typically used to depict keyword metadata (tags) on websites, or to visualize free form text. Tags are usually single words, and the importance of each tag is shown with font size or color. This format is useful for quickly perceiving the most prominent terms and for locating a term alphabetically to determine its relative prominence. When used as website navigation aids, the terms are hyperlinked to items associated with the tag.