My wife's definition of 'teaching to the test', which she says is shared by most of her colleagues: teaching the kids the possible questions and answers for a specific section of the standardized test. In other words, the teacher does not know that a question will ask about the capital of Canada, but may know that a common geography question is name the capital of a country in North America. You don't know which equation, numbers or operations will be on the test but know that the math section usually has questions about how to solve an equation with a certain sequence of operations. Or the Language Arts section will likely have a question about how to write a topic sentence.
She says teaching to the test will be much more difficult with the Common Core Smarter Balance Assessment since it will be given by computer and the test questions will get more or less difficult depending on how you answer a given question. The material being tested on will be much broader and there are thousands of possible questions for any one grade level for all the subjects. She is on some sort of national taskforce that is writing questions for the Smarter Balance Assessment, which is intended to be a nationwide test.