I have seen many people use the phrase "my bad" in Internet forums. What does it exactly imply and is it a proper English phrase?
Yes, "my bad" is a proper English phrase. It is an apology; when you say "my bad", you're basically saying, "I admit a mistake" or "my fault, sorry for that". Wiktionary says:
(colloquial) (idiomatic) My fault; mea culpa.
- Yes, I realize the humvee isn't supposed to be parked in the heirloom flowerbed. My bad.
It also links to this Language Log entry, which provides further insight:
The authoritative discussion of the phrase "my bad!" at this Random House site says it originates in pick-up basketball as a phrase used by young urban players when admitting to an error. It has spread to other domains and is now used widely to mean something like "I admit that I have made a mistake." It was nominated for "word of the year" (not that it's a word, it's clearly a phrase) in 1999, but in fact it was already at least twenty years old by then.
Concrete Gannet is right. "my bad" is very much an Americanism. I had not heard this until recently, and was baffled when I did. I heard it on American television programmes and a computer game. I have not heard any British people use it.
To me, it's like the Americanism "I could care less". It does not actually, make sense. It might be acceptable and even considered as proper English in the USA but, it is not elsewhere. At least not in the UK. It does not make sense because, it is an unfinished sentence.
When I have heard it, my immediate thought was, "your bad what?". Your bad behaviour? Your bad language? Or, just your bad English, which this sentence demonstrates?