Mostly used to highlight something and proclaim shock, respect or to garner agreement.
Informal, and used mostly by gangsters, youngsters or the less educated.
Did you see Jack's new girlfriend? Damn hot sia!
Check out his track record! That's not even humanely possible sia!
SIA is basically a Gaming term in computer world, refering to real life term - KIA.
It's very alike with word skillad, meaning Skilled In Action. It's Killing with Skill = S-killing.
Being SIA in first person shooters has a meaning of being shot in a very unorthodox, very thought through and amazing way.
SIA can be anything including Headshots, Clutches, ACEs, and other amazing stuff that can be done using skill.
SIA'd also may have a meaning of " Served in action " linking to " you got served " .
(two guys watching their teammate frag):
- Woah, look at that HS !
- Ahahaha, another one !
- Holly shit, those guys got SIA'd :DD