What is 12345?
1.
This is said when you agree with something being said, usually a strong negative statement or comment about something else but not always.
its commonly used on online chatting forums and can mainly be found on thecomeupboard/forum/ where the word was originally created.
same as: yep, ya, word, hella true, fo sho
example 1
guy 1: dude this class fucking sucks!
guy 2: 12345
example 2
guy 1: check out that ass, id hella tap that
guy 2: 12345
See
2.
The combination an idiot would have on his luggage.
His luggage combination is 12345.
See
3.
Used on message boards, '12345' is often left as a reply to users who have made idiotic replies/posts and, quite simply, means, "no shit dumbass". The origin of '12345' is from idiotic people who make their passwords 12345 (or any other password that's easy to figure out).
message board user #1: Did you guys know that the world is round and not flat?!?
message board user #2: 12345
See