When males' testicles or balls or gonads retract and shrivel. Sometimes due to cold or excitement but primarily in this case due to fear and anxiety.

Like two little turtle heads, connected by skin and sinew, pulling back into its/their shell.

Metaphorically similar to a poo shy turtle but technically, physically and emotionally a very different experience.
She was fun, interesting, sexy and his friends wanted to bone her, but the fact that she was clearly cleverer than him gave him a siamese shy turtle. Would she notice? Would she care if she did? Or, does the fact that even imagining approaching her makes his body eat his balls mean that he'll never have the courage to get close enough for his shriveled sack to matter?

"You know that Bobbitt story, right?"
"Awh, man, don't maaan. Giz me a siamese shy turtle just thinking about it"
by RastaVari October 23, 2013
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The previous name for Betta fish. Since activists want to make sure any sign of creativity and originality is eradicated off the planet because it's "unsafe".
In Texas a 10 year old can buy an AK-47 with no problem at Walmart but activists made sure to get rid of the Siamese fighting fish because it's a "safety hazard".
by AcneAndAnthrax November 30, 2014
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When two or more parties touch and rub their buttholes together. This is not only platonic, but extremely heterosexual as well.
Keithan: "I was cuddling in the bed of a Ford F150 with 36 of my closest homies, and we ended up all Siamese French-Kissing."

Daveth: "Dude, I wish I was that straight and platonic with my 36 closest homies."
by Iva Smallsach December 17, 2021
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when 2 people press their buttholes tautly against each others, and one person farts into the other's butthole
Last night, Frederico gave me a siamese whoopee cushion. It was even better when i blew it back into his butt.
by the wundatwinz December 24, 2005
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The act of fornication with Siamese twins conjoined at the vagina.
Dude I totally gave those bitches a Siamese Beef Injection last night!
by beefinjection September 23, 2010
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When a female puts her nostril on the males urethra and the male urinates and the urine goes up one side of her nostril and comes out the other side, therefore creating the sinus flush.
“Wow, did you hear John gave Becky a Siamese sinus flush?”
by Jackatee March 20, 2021
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