When a woman has an orgasm so intense her legs become like jelly, possibly resulting in her falling over. Often accompanied by a Squirt
Laura: I'm telling you, sit down when you jill off in the shower.
Sarah: Why?
Laura: Because if you do it right you'll get Jelly Legs and you don't want to hit your head on the way down.
When a child goes into a state of paralysis below the waist in order to get what he/she wants.
Kid: I WANT CANDY!!
Mom: No!
Kid: I WANT CANDY!(Kid goes into jelly legs mode)
Mom: Timmy stand up! I'm not going to carry you!
Kid: WAAAAAAAHHHH!
Mom: Jesus! Here...what do you want?
The ability girls and women have developed to hold several items at once in one hand. The skill has been developed due to the lack of pockets in women's clothing.
I thought she'd need multiple trips to carry her phone, keys, wallet, and Starbucks to her car since she needed the other hand to open the door, but she used her impressive girl grip to carry everything in one hand.