A shortening of autism and can be used as a nickname, or often a group of absolute fuckwits.
Tism number one: "Tism number three what the fuck are you doing?"
Tism number three : "sorry tism number one, just looking at naked ladies"
Random user of the tism : "absolute fuckwits."
War thunder is a game that is complete hell and makes you wanna die.
person number one: "SHIT DEPLOY FLARES TISM 2"
Tism 2: "FUCKFUCKFUCK NEEEEEEEEEEEOWWWWWWM BANG *fucking explodes due to war thunder AIM-9 sidewinder*"