Tighter than a Cat's Ass 

Intensely tight to the point that entry seems impossible

"Due to the visit of a foreign dignitary, the police had the city locked down tighter than a Cat's ass!

Tighter than a Cat's Ass by Mr. Jameson September 14, 2010

tighter than a duck's ass 

Impermeable. I.e., watertight.

My English teacher is tighter than the proverbial duck's ass.

tighter than a duck's ass by octopod March 4, 2004

tighter than a clam's ass 

Excessively cheap and tightfisted with money.

Forget about asking John to donate. He's tighter than a clam's ass.

tighter than a clam's ass by JerseajersJea60 June 24, 2017

tighter that a mosquito's ass stretched over a rain barrel 

Used to describe the tightness of a womans vagina to all your friends. Often used in conjuction with the words likepussy, cunt, and box. BEWARE! NEVER USE IN FRONT OF WOMEN TO DESCRIBE OTHER WOMEN. DIRE CONSEQUENCES MAY INCUR!

Her cunt was tighter that a mosquito's ass stretched over a rain barrel... niccce!

tighter that a mosquito's ass stretched over a rain barrel by Jeep_Junkie March 13, 2007

Tighter than a crab's ass 

This is an insulting and derogatory description for somebody who is very, very cheap. It's believed that crab's asses are rather compact, so someone tighter than a crab's ass is about as selfish/cheap/greedy as it gets.

Jake: Bill by the way, what did you leave our waiter?
Bill: 15%.
Jake: Christ Bill you're tighter than a crab's ass. I have to stop eating with you if you're going to embarrass me like that again in public. That poor waiter worked his ass off you cheap fuck.

Tighter than a crab's ass by Space Wrangler August 24, 2021

Tighter than a nun's asshole. 

Very tight. Allows nothing to pass through. invulnerable to penetration

This wine is tighter than a nun's asshole.
a nun is a woman who dedicates her life to the Catholic religion and marries Jesus, but is not allowed to love a man in real life, so people think nuns are very strict, unhappy, and tense. Tense people are sometimes constipated, meaning unable to defecate, or their asshole is blocked with something.

Tighter than a nun's asshole. by jo3schmo3 May 3, 2009