BA

Depending on context may stand for 'Bad Ass' , 'Bachelard of Art' or 'Breast Augmentation'. Honestly I have never seen it to be used for 'bad ass' as everyone here seems to be suggesting but there you go.

What should be used for bloating/constipation after BA (breast augmentation) surgery?

You are a real BA (bad ass)

He has recently finished his BA course in photography.