In Finance:
* Individual Savings Account: This is the most common meaning in the UK.
* Investment Savings Account: This term is sometimes used in the US.
In Technology:
* Internet Security Agency: A government or private organization that provides security services.
* Instruction Set Architecture: Defines the instructions that a computer processor can execute.
* Intelligent Systems Architecture: A framework for designing intelligent systems.
In Other Fields:
* Independent Schools Association: A group of private schools in the UK.
* International Security Assistance Force: A NATO-led security force in Afghanistan (formerly).
* International Standards Association: An organization that sets standards for various industries.
* Internet Service Access: A general term for accessing the internet.
To know the exact meaning of ISA, you need more context. For example:
* What is the subject of the discussion? (finance, technology, etc.)
* What is the location? (UK, US, etc.)
Let me know if you can provide more information, and I can help you find the right full form!