Unfollow is, of course, a straightforward derivation of follow using the prefix un-, conventionally added to verbs, adverbs and adjectives to give the opposite meaning (e.g. unhappy, untie). Defollow is a common lexical variant (formed from prefix de-, which also denotes opposites, e.g. decaffeinated, deactivate). Both words mirror derivational activity in the lexicon of the social networking site Facebook, where users who remove someone from their list of friends are said to unfriend or defriend them.