Idk means i don't know. If someone texts (asks in messages) you a question you don't know, you simply text back ''IDK''.
''Do you know what's 20\2?'' idk.
Bob: what does idk mean?
Dima: I DONT KNOW
Bob: oh, thats a bummer
Dima: NO BOB, IT LITERALLY MEANS I DONT KNOW YOU DUMB FUCK
Bob: okay ill ask Andrew since you still dont know
the form of a saying I do not know for the smart and unfunny cunts who don't understand the fucking joke
Brett: Yo Quaver can you go to the movies.
Quaver: Idk Brett
Brett: What dose idk mean?
Quaver: This nigga
idk means I don't know
Person 1: You coming to my party?
Person 2: Idk.
idk means i dont know. which means you don't know anything because you suck. joking i suck too.
Joe: what are you doing today You: idk