Initialism of Responsible Service of Alcohol (a qualification and permit for bar staff).
"The new bartender passed his RSA exam to get certified in responsible service of alcohol."
In plain English: RSA is a secure method computers use to send private messages over the internet without anyone else being able to read them.
"The RSA was established to provide security services for its members and customers across Europe."
Initialism of Royal Society of Arts.
"After winning his award from Rsa, the architect was invited to speak at their annual conference in London."