mad

Mad has two everyday meanings and they belong to different countries. In Britain it usually means insane or wildly foolish — a mad idea, gone mad, mad about a hobby. In America it usually means angry: don't be mad at me.

That split is the single most useful thing to know about the word, because British mad at somebody sounds like a mistake and American mad meaning insane sounds old-fashioned. Both dialects share mad about, meaning enthusiastic: mad about horses. On register: mad for insanity is informal and now often avoided when talking about actual mental illness, where the polite words are different. As an intensifier it is common and harmless — mad keen, driving like mad.

Phrases it lives in

• like mad — as hard or as fast as possible, with no attempt at restraint
• drive somebody mad — irritate them past the point of patience, usually by repetition