Real Interest Rate turning Negative and its implications

What is a negative real interest rate? 
The real interest rate is the effective rate after adjusting for inflation and is considered a true measure of the cost of funds for the borrower or the return to the lender. It is calculated approximately by subtracting the rate of inflation from the nominal interest rate. When inflation is higher than the interest rate, the real interest rate becomes negative. If the one year interest rate is 8% and average inflation over this period is 10% then the real interest rate is negative 2%.

Price Deflator

A deflator is used to convert data compiled over a period into prices prevailing at an earlier point in time. for example, the current price of a television can be deflated to what it would cost say three years ago.
GDP Deflator, on the other hand, is a comprehensive measure of inflation, implicitly derived from national accounts data as a ratio of GDP at current prices to constant prices. While it encompasses the entire spectrum of economic activities including services, it is available on a quarterly basis with a lag of two months since 1996. Essentially, a deflator removes the effect of inflation from data, making it comparable across periods.