Wind someone up
What it really means
To tease someone or deliberately annoy them as a joke. "Is this a wind-up?" means "is this a joke / are you tricking me?".
Context, tips & common mistakes
A wind-up is a tease built on false information — telling you the exam moved to 8am, that the office closes early on Fridays — sustained just long enough to watch you believe it. 'Are you winding me up?' is therefore the standard British phrase for 'is this actually true?', useful daily, and a 'wind-up merchant' is someone who does this professionally among their friends.
When you discover you have been wound up, the winning response is laughing and promising revenge; visible annoyance hands the room to the merchant. Being chosen for wind-ups is, confusingly, usually affection — strangers are not teased. If a claim genuinely matters (money, deadlines, visas), verify it independently rather than relying on your ability to detect the completely straight face Brits maintain while lying for fun.