To take someone off your list of friends on a social networking site. Informal internet talk, born with sites like Facebook in the 2000s. You defriend a person; the friendship on that site is then gone. Though actually, many people now say unfriend for the same act, and that form has won in a lot of places — both are understood, but defriend can sound a little dated. It is not the same as unfollow (you stay friends, you just stop seeing their posts) or block (much stronger: they cannot reach you). You would not use it in a formal letter.

刪好友、解除好友（社群網站上把人從好友名單拿掉；現在更常說 unfriend）。