Merriam Webster's Dictionary: Tax -- "a charge, usually of money, imposed by authority on persons or property for public purposes."

In the most contentious exchange of President Barack Obama’s marathon of five Sunday shows, he said it is “not true” that a requirement for individuals to get health insurance under a key reform plan now being debated amounts to a tax increase.

But he could look it up — in the bill.

Health bill says 'tax' when President Obama said 'not'