Here's a breakdown:
* Oui: Yes
* mon amour: my love (a term of endearment)
* très: very
* amusant: amusing, funny
The phrase conveys a playful and affectionate tone, suggesting that the speaker finds something the other person has said or done to be amusing.
It's important to note that the spelling is slightly off in your question. The correct spelling is "amusant," not "amusnt."