To wrongfoot someone is to catch them off balance — to do or say something they were not ready for, so that for a moment they do not know how to answer and look a bit foolish. Often written 'wrong-foot' with a hyphen; both spellings are used, and it is a verb: wrong-foots, wrong-footed, wrong-footing. The picture comes from sport. In tennis or football, you send the ball one way while your opponent's weight is already going the other way — their foot is on the wrong side, and by the time they turn, it is too late. English keeps that picture for arguments, meetings, politics and interviews: an unexpected question, a sudden change of plan, or news nobody was told about can wrong-foot people. So it is not the same as 'trick' or 'cheat'. Nothing dishonest has to happen. The person is simply not prepared, and the surprise puts them at a disadvantage. It is common in the passive — 'the government was wrong-footed by the announcement' — and in British writing especially. It is more common in newspapers and formal talk than in daily conversation, where people say 'she caught me off guard' or 'that threw me'.

打亂陣腳、殺個措手不及、讓人措手不及而慌了手腳（原是網球、足球術語：把對方重心引到錯的一邊）