This author has an interesting take on the subject (the article has more examples about his point):
While the ostensible purpose of the Federal Reserve is to “stabilize” the money supply, its real purpose is to enable public officials to spend as much money as they want by borrowing it and then letting the Federal Reserve pay off its creditors with newly printed, debased, cheapened, devalued dollars.
That's precisely what the Fed is doing now, has been doing recently, and has been doing ever since it was established in 1913. It “monetizes” the government's debt by printing the money to pay it off. The inflated supply of money cheapens the value of the money in circulation, which means that bondholders are being repaid in currency that is worth less than it was when they loaned it.
That's a default.