Obamanomics is a neologism which seeks to define the economic philosophy of the Obama administration. The portmanteau has obvious historical references to "Reaganomics", which is commonly used to define the policies of President Reagan in the 1980s.
Less obvious, however, is agreement on what Obamanomics actually means. To conservatives, the term is used negatively to describe an increasing role for the state. Democrats, meanwhile, cite health care reform and cap-and-trade as positive examples of Obamanomics.
The reason why the term is difficult to define is because the Obama administration was thrust headfirst into the financial crisis and recession. Emergency measures are being confused with a new economic philosophy.