(verb) A crime where a drug dealer befriends a weak, old or otherwise vulnerable person, then takes over their home and uses it as a crack house.
"Cuckooing is a new type of crime which involves a drug dealer befriending a vulnerable individual who lives on their own.

Like a cuckoo, the dealer moves in, takes over the property, and turns it into a drugs' den."

(BBC Inside Out, March 23rd 2007)
by Andy January 20, 2008
Have lost ones mind, gone nuts.
After studying so much, I have gone cuckoo.
by Tara February 24, 2004
Someone who has lost the plot and has no idea what time of day it is. Often talks incessantly about nothing in particular, regardless of whether you are listening to them or not. Also bonkers and hatstand.
You know Nichola King? She's totally cuckoo
by Craig May 10, 2004
To act crazy and foolish.
Person 1: Did you hear about that girl the other day?
Person 2: You mean the one who acted like a little child and was bouncing off the walls?
Person 1: Ya. She must've had a lot of sweets that day, she was really cuckoo.
by Gamemaster2468 February 17, 2017
Noun: A Cuckoo is a person who acts in a similar way to the bird of the same name.

Generally by entering a friend's home (always a friend, otherwise that person is known as a burglar or psycopath) and eating their friend's food, using their stuff and sleeping in their bed, a person can be described as a 'Cuckoo'.

A person who is a Cuckoo may also attempt to subvert a friend's parents to their own greedy whim, making them believe he or she is needy, and in doing so neglect their biological offspring in order to feed, clothe, house and entertain the Cuckoo. Note. Cuckoos are normally ginger, quite immature, and hated by all who know them.

Ajective: (-ier,-iest).

Below: People do not have to be actual Cuckoos in order to be described as having Cuckooed something for example. Only in the most serious cases is a person actually a Cuckoo.
Verb: Cuckoo. To 'Cuckoo' something belonging to another. Basically acting as a Cuckoo and taking, using, or eating something belonging to another.
Past tense: Cuckooed. Something taken, used or eaten by a Cuckoo in the past.
Present tense: Cuckooing. When something is being taken, used or eaten by another.
Future tense: Cuckoo. If it is known that a person will take, eat or use something in the future.
Daddz - "Jesus fucking Christ, Andrew has eaten all the mayonnaise again!"
George - "I know, he's a fucking Cuckoo isn't he."

Lizzie - "Andrew has cuckooed all the bread!"
Daddz - "Not a suprise really is it... he's the cuckooiest Cuckoo I know."

Larry - "Oh for fuck sake, that fucking Andrew has gotten into the buscuits again!"
George - "Well fuck me sideways... what a fucking dirty Cuckoo bastard!"

Teddy - "Quick, stop him! He's Cuckooing all the beer!!!"
Larry - "Fucking Cuckoo!"

George - "You'd better hurry home, I dropped Andrew back there about 20 minutes ago. You know what happens when you leave a Cuckoo in your house unattended."
Lizzie - "Oh shit... oh shit, shit, shit, fucking shit! He'll fucking eat the cake my mum made earlier, shit!"
George - "What a fucking arsehole Cuckoo! Yeah you need to get back there, he'll probably shit everywhere afterwards too!"

Andrew - "Lizzie's parents think im the fucking dogs bollocks. What a pair of utter tits. Im going to steal all their food while they're out and blame it on Lizzie while I roll around in Lizzie's bed, too fat to move."
Another unknown Cuckoo - "Fucking awesome mate, yeah they do sound like complete tards."

George - "God fucking dammit! Can't you see that Andrew is a Cuckoo? He's sleeping in my fucking bed... Mary Mother of Jesus what the fucks wrong with you?!?!"
Mother - "Oh that Andrew is such a good little boy, I wish he was my son. His parents must be so mean to not feed him properly."
Andrew - "Cuckoo!"
George - "Look! He just did it again! Didn't you fucking hear that? Oh Jesus Christ you stupid fucking bitch-whore, cunt, arsehole, cumbucket you really are a retard!"
by Aryan1987 August 9, 2008
A word used to break the concentration of the free-throw shooter in a game of basketball. Exclaimed in falsetto.
Player 1: (begins to shoot free-throw)

Player 2: "CUCKOOOOOOO!!!!!"
by seussb_d April 8, 2006
A person who waits around to steal your lover from you at the first opportunity.

The cuckoo, who usually plays the role of being a "friend", is likely to be a friend of your significant other's best friend's partner. They use the convenience of "let's go out as s foursome" as part of their swooping technique.

Just as the real cuckoo waits for an opportunity to get into another bird's nest, then throws out their eggs and takes it over as their own. The cuckoo swoops in, and starts dating your partner.
"I knew that Dave bloke was sniffing around and wanted to be more than her friend. Fucking cuckoo stole my nest!"
by Abcd432 October 17, 2015