As a member "IPSA" means to me the International Political Science Association, an excellent body that promotes research and understanding of politics. But is has a different meaning for MPs at Westminster - it means the "Independent Parliamentary Standards Authority". It has received much criticism - and some MPs have been caused some considerable problems as a result of its procedures.
The House of Commons Library has produced some research notes on IPSA - press the link to see them
The Publication of MPs Expenses by IPSA
IPSA: Operating the Members Expenses Scheme
The establishment of IPSA