A notch is a piece of eyebrow missing due to a razor.
How it occurs:
1. Person A makes a boast about something they will due
2. Person B says "notch"
3. Person A must then do the thing that they boasted about or else Person B will get to take a piece of their eyebrow

Notch: Another word for Jesus.
Anyone who play minecraft know him.

Something being of good quality. As in Top Notch

(Verb) To inadvertently DDoS attack a website due to sudden interest, often caused by a reccomendation from someone with many online followers or fans.

Coined on the 26th August 2011, when popular indie games developer Notch (Markus Persson) directed his 300,000 or so twitter followers to visit the website of Grimrock, another indie game, almost immediately crashing it.

A notch is a very unspecific unit of measurement.

Hot, particularly good looking, dank

A notch is a unit of measurement for sexual partners. Some people count anything more than kissing as a notch, and some people only consider sex as a notch. They are a count of how many people you have hooked up with, and not how many hook ups you have had.