Definition of unfriend in US English:

unfriend

verb

[with object]informal
  • Remove (someone) from a list of friends or contacts on a social networking website.

    ‘she broke up with her boyfriend, but she hasn't unfriended him’
    • ‘That last word, unfriend, is in fact, the word of the year.’
    • ‘So if you don't respect me or my opinions you can unfriend or defriend me.’
    • ‘He told me he's noticed an increase in people threatening to "unfollow" (or unfriend / un-subscribe etc.) from his feed.’

Pronunciation

unfriend

/ˌənˈfrend//ˌənˈfrɛnd/