My bad
Definition 1 of 1
Pro Tip 1/3Apology Light
Use 'my bad' for minor errors or when a casual apology is sufficient. 
Dropped your pen? Pick it up and say, 'Oops, my bad!'
Pro Tip 2/3Casual Tone
'My bad' is informal and commonly used among friends or peers. 
If you forget someone's name in a social setting, you can say, 'Sorry, my bad!'
Pro Tip 3/3Not for Serious
Avoid using 'my bad' for serious mistakes; it may seem insincere. 
If you break someone's valuable item, don't just say, 'my bad,' offer a proper apology.