Test suite pollution is when one or more automated test cases deliberately are allowed to fail in a test suite. This usually leads to the executing test suite to be un-attended since errors are expected, a very unfortunate situation during development. New defects surfacing can easily be missed out and the longer the test suite gets ignored recovering it to stable can be cumbersome.
This is just an attemp to clarifying one of the ‘buzz’ terms I preach to my team. Please correct me if you think I am out of line.