The meaning of "bring it on" is:
The definition of "bring it on" is:
(idiom) let’s see how good you are
The football team challenged their rivals to bring it on as they ran onto the field.
A: Your girlfriend is ugly.
B: What did you say?
A: I said, she’s ugly.
B: Do you want to fight?
A: Bring it on!!
bring it on is usually used before challenging someone to a competition or fight