Leg boner 

A leg boner occurs when one's legs stiffen, usually for a couple of days, making it awkward to walk, run etc. It is most likely to affect a person when their significant other / crush is nearby.
The most scenario of a leg boner environment is a sporting activity, with the s/o or crush in the same team as them.

Jessica got a leg boner during Physical Education because Sheldon, her crush, was in her team for the game of Rounders. It took her a few days to recover fully from it.

Leg boner by Pickapon August 18, 2014

Leg Boner 

A leg boner occurs either in the dead of the night or at random times during the day where either you are sleeping or just sitting criss cross In the floor where the back of your thigh catches a cramp thus having to spring your leg up into the air to stretch it out.

“Ahhhhhh fu.... LEG BONER!!”

Leg Boner by D'Rack2Times November 12, 2017

Leg Boner 

When a new guy in soccer is so excited to kick the ball they kick it as hard as they can out of the field.

Guy 1: aww man, that kid over there has a huge leg boner.
Guy 2: I know, stupid noobs, they piss me off.
Guy 3: I remember my first leg boner, but I was 5 so its all good.

Leg Boner by ytryf7 October 30, 2011

Leg Boner 

1) What happens when you are in extremely close quarters (i.e. a hug) with someone and you get an erection their leg.

2) A true test to see if a girl's into you.

1) Guy 1: So I was hugging Tina today...
Guy 2: What happened?
Guy 1: I got a leg boner and I think she liked it!

2) Guy 1: I think Tina likes me but I'm not sure.
Guy 2: Use the leg boner test.

Leg Boner by Pudge/Kyle October 16, 2008