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6.
unbelievably sexy, near orgasmic lower back
Jenny's psis is the most beautiful thing in the world.

Lower back right near the dimples.
by ynnej zruk March 31, 2008
 
1.
PSI
per square inch

sometimes used in paintball
when using or playing paintball and HPA *high pressure air* their could be 850 psi in a pb tank
by viva la vidaa May 06, 2009
 
2.
PSI
Common abbrevation for Psionic Energy,
it can also be used as the name of a catagory of skills, often called Psionics.
When you make a PsiBall, you can feel the Psi running through your body.

How long have you been doing Psi?
by PsiZero November 06, 2003
 
3.
PSI
The letter in the Greek Alphabet that comes after chi and before omega.
alpha, beta, gamma, delta, epsilon, zeta, eta, theta, iota, kappa, lambda, mu, nu, xi, omicron, pi, row, sigma, tau, upsilon, phi, chi, psi, omega
by The Cobbgoblin May 16, 2006
 
4.
PSI
Pussy per Square Inch. This is an international standardized unit of measurement for square inch of pussy applied to square inch of penis/penii upon penetration. Higher PSI is related to but not conclusive of: better sex, increased number of orgasms, increased intensity, more sexual partners, and a higher probability of contracting an STD. Queefs are also more present in a female with higher PSI, although no direct correlation has been found. The mathematics to define PSI are listed below:

(Penis(Surface Area)/Vagina(Surface Area))*((Penis(Circ)-Vagina(Circ))/100)*Penis(Circ)*Penis (Length)*(Penis(Length)-Vagina(Depth)/100))

Example Math:
Jew Penis: Length: 10inches Circumference: 9.42 inches Surface Area 94.2 inches squared

Twelve Year Old Vietnamese Girl: Depth: 3.5 inches Circumference: 3.14 Inches Surface Area: 10.99
8.6*.063*94.2*.065 = 3.31

In this example, the Jew Penis would feel the pressure of 3 normal pussies on his erect penis during intercourse. This would be amazing.
No children were harmed in figuring out this information.
I could never get with a Jew Penis again. Last time there was so much PSI I wish I had a blow off valve.

I really want to rail that girl over there and take her for a ride. I feel like my boost meter could hit over 10 PSI.

So what do you think our PSI would be baby?

I may not be that big, but I'm an expert with Maths and can tell with your small vagina there would be plenty of PSI.

OH MY PSI. It's over 9000!

Fur and Loathing in Miami: That fox and cat managed to achieve 12 PSI through strategically places holes in their fur suits.

That can't be right, my PSI is reading less than one with an Asian girl. Shit, I should go to the doctor tomorrow.
by PSICAT October 20, 2011
 
5.
PSI
Pounds per square inch.

If used in the form "That person has a high PSI". It is a sexual reference saying there ass or another part of the body where a penis can be inserted is capable of taking alot of pressure, or quite a hard pounding. Can also reference to the largest penis they can fit in their ass before the pressure gets to high and rips it.
That h0 has a really high max psi.
by Anonymous February 24, 2003
 
7.
PSI
A sex ed program in public school in which teachers who probably haven't actually had sex in about 20 years teach you to keep your hands and other parts to yourself. Sometimes guy will get lucky and have a hot PSI teacher, which makes for an interesting experience.
"Damn, we've got PSI today!"
by Losti March 21, 2005