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When you see someone you dislike or have a problem with and you guys automatically break out into a scrap upon seeing one another.
1. "If that guy comes through its on sight"

2. "I saw that Evan guy at a party and it was on sight"
by AirMtb May 29, 2016
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3
A term in rock climbing, describes completing a lead route without falling. The climber must not know anything beforehand about the route or have watched someone else climb it. See flash and redpoint.
I made the first ascent of this route by onsighting it because it was probably only a 5.7.
by sano September 21, 2003
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4
When there is no money being made off it, most people that talk about on site shit aren't going to do anything but bait somebody into a possible jail visit over what they say or do in response to being antagonized by some pussy.
D tried to get all his friends to come watch the fun of getting this crackhead dude locked up for saying or doing something really stupid on sight.
by Michael "the Shocker" Pulaski September 22, 2018
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5
A good way to turn someone into a YouTube star, pretend you want to fight them and have a friend film it.
The two girls pretended to almost get in a fight on sight and claimed they were doing for you, the viewing audience.
by Michael "the Shocker" Pulaski September 22, 2018
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