My word I've personally used since 1997 to replace 'cool.' They said cool in the 50's and it needs to die. It now just means Okay. Screw that. Awesome and the like are trying to step up, but they don't work for me either.
Jast originally came from the name of an adult japanese rpg company. Their game came on a pirated game cd from Pakistan.
Their logo was a red JAST on a pink ground. A blue haired girl with a fox tail winked at you to the right.
Any celebrity news is not jast.
Yo-yos were jast in third grade.