A lunatic is a person who behaves in a crazy, reckless and often dangerous way. It is an informal word: He drives like a lunatic. It does not mean someone who walks in their sleep: that person is a sleepwalker, and the condition is called sleepwalking.
lunatic: will you get the meaning right?
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drive/behave + like a lunatic; a complete + lunatic; a lunatic + idea/plan; a sleepwalker / sleepwalking (not lunatic)
- My neighbour thinks I'm a lunatic for swimming in the lake in November.
- He was shouting at the printer like a lunatic because it had eaten his report.
- Hiking up the mountain in flip-flops was a lunatic idea, and we soon regretted it.
What changed
First versionMy little brother is a lunatic: he walks around the flat at night in his sleep.
RevisionMy little brother is a sleepwalker: he walks around the flat at night in his sleep.
In some languages, a word that looks like lunatic means sleepwalker. In English, though, my little brother is a lunatic sounds like my little brother is crazy. For someone who walks in their sleep, English has a separate word, sleepwalker. There is a verb too: He sometimes sleepwalks.
Lunatic sounds strong and emotional. You might say You're a lunatic! to a friend after something reckless, but you must not use it about people with mental illness: that is offensive. For a strange or risky plan, crazy is milder: a crazy idea.
Your turn
A man on a motorbike was racing through the park at full speed, like a complete ___.
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lunatic — The motorcyclist is racing through the park at full speed, which is reckless and dangerous. That is a lunatic. A sleepwalker is someone who walks in their sleep, and the word does not fit someone racing through a park.
Describe a time when someone on the road behaved recklessly. Say where it happened and what exactly the person did.
On a narrow country road near Kazan, some lunatic overtook three lorries on a blind bend.
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