Iakt

1). I already knew that
OR
2). I already know that
typically to tell a someone you already know something and you thing the wannabe nerd telling u the info is stupid for telling you that (actually nah, it litarly means i already knew that/know that and can be used on anyone)

cyberbully: your a dumbass
me: iakt
cyberbully: you roasted yourself lol
me: iakt
someone in gd daily chat: you can make a cat by typing "^0U0^
me: iakt