Acting silly, goofy, or dumb. Usually used in insulting manne. Can be spelled sillyen or sillyin.
The man was told to stop sillien around.
National Fighting Day is on October 26th. Feel free to start fights with anybody you see.
Guy 1: Hey bro, you know what day it is?
Guy 2: No, why?
Guy 1: It's National Fighting Day
*Guy 1 knocks Guy 2 out*