Pareto  

Pareto efficiency is enforcing something that makes somebody better off without making anybody else worse off. Net society gains as a whole.

It's like 2 guys chasing 2 girls (a blonde and a brounette). Guy 1 only likes blondes. Guy 2 only likes brounettes.
Outcomes:
Guy 1 gets both girls. Guy 2 no girl.
Guy 2 gets both girls. Guy 1 no girl.
OR,
PARETO EFFICENT OUTCOME:
Guy 1 gets the blonde, and Guy 2 gets the brounette. Each is made better off without making the other guy worse off.

Pareto by C.Brown February 6, 2008

pareto- 

Roughly but not exactly.

Like, when you say pareto-80 you don't exactly mean 80 percent, you really mean, roughly four out of five. Pareto-20 means one out of five, and saying that a scheme will likely fail at pareto-5 means it'll go okay so long as we don't roll a natural 1.

So, like, 20 percent of respondents say that—

That's bullshit, you pulled that number out of your ass.

Pareto-20, man. You're right, it's... (checks notes) closer to 18 percent, but that's not much of a difference, is it?

pareto- by tariqk July 13, 2022

Pareto Optimal 

When two guys work as a team instead of independently to hit on women; thus getting more and far better looking women than they would have apart.

See Wingman or Wingmanning

Working together, Kevin and I talked these two girls who should have been out of our league into joining us for an Eiffel Tower - it was so pareto optimal.

Pareto Optimal by Ryanatcollege May 16, 2005

Pareto’s Poop 

The theory that one completes 80% of their poop in the first 20% of their bathroom time.

You were in the bathroom for an hour; by the laws of Pareto’s Poop you really needed only 12 minutes.

Pareto’s Poop by alghazali320 July 8, 2019

Pareto's Iron Law

The Italian sociologist living in the early 20th Century observed that the distribution of wealth and income remains roughly the same in modern industrialized societies no matter what governmental policies are pursued. A corollary of the Iron Law is the "circulation of elites" where groups vie to be the dominant group under various guises including equality and social justice, but there is always an elite no matter what.

Liberal elitist humanitarian: Let's pass legislation to make a more equal, fairer society.

Conservative realist: That will get us no where except you leftists will be in power rather than us. There is the brutal fact of Pareto's Iron Law. We cannot escape inequality of result.

Liberal elitist humanitarian: Well, I know, but at least we will be ahead of you conservatives. We hate you because you do not love everyone as we leftists do.

Pareto's Iron Law by Tex in Tex February 25, 2008

Pareto optimal 

A sophisticated way to say, "Life is not always fair"

Person A: How come Hillary Clinton didn't win the 2008 primaries?

Person B: Well...life in many ways is Pareto optimal. Besides I heard from someone that her campaign slogan was, "Anarchy is my policy for men."

Pareto optimal by paisleynotes November 2, 2009

Pareto part

The main source of value or importance in something being considered. The Pareto principle is that 80% of the effects come from 20% of the causes, sometimes shortened as "the 80/20 rule"

YOU: This yard is full of weeds. It'll take us two days to clear them out.
ME: Let's just do the Pareto part surrounding the walkway: that should only take 4 hours and 48 minutes.

Pareto part by billbrown October 10, 2023