Similar words: loon, balloon, saloon, doubloon, pantaloon, balloonist, trial balloon, pony. Meaning: ['luːnɪ] 
n. someone deranged and possibly dangerous. adj. informal or slang terms for mentally irregular.
n. someone deranged and possibly dangerous. adj. informal or slang terms for mentally irregular. 
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1. What's she up to? She's as loony as her brother!
2. He does have some pretty loony ideas.
3. He had lots of loony ideas about education.
4. At first they all thought I was a loony.
5. Her brother's a complete loony.
6. It was Day Release at the loony bin.
7. Make that three wounded and one loony on board.
8. Your average loony racehorse can do better.
9. Billy was loony with time-travel and morphine.
10. Janet's brother is a complete loony.
11. He's an absolute utter loony.
12. Political loony, surprised thief, old lag with a grudge ... it's facts I want, not surmise.
13. That loony leftover of a nation surely won't stagger on much longer-and anyway it's suspended its missile programme.
14. She felt like a total loony doing these things for herself.
15. What kind of a loony bin have they got down there in Berkeley, anyway?
16. What of the loony fringe that I had so conveniently forgotten?
17. Perhaps that means it's raising money for a loony bin.
18. I can't be loony if I can remember my dream, surely?
19. On the floor above the loony bin, nobody quite knew what took place.
20. Malthus thought their more-the-merrier theory was hopelessly loony and downright dangerous.
21. The bloke who made up those tests was the real loony if you ask me.
22. Make one misstep marketing creamed corn and you could end up in the loony bin.
23. Collision He's making me out to be some sort of thick, brainless loony on a self-destruct road to ruin.
24. The best he can manage with this script is a sense of loony bigotry.
25. He said I waved at the poor man like a loony.
26. A bit tricky under the circumstances, although I've never actually done it with a raving loony.
27. Major was spot on, just as he was dead right to go on to warn Hague against his loony right.
28. They felt free to festoon the machine with all sorts of loony filigrees.
29. One of the most worrying aspects is the danger posed by irresponsible and loony left local authorities.
30. Even if it wasn't quite enough finesse to keep him out of the loony bin.