Nice definition of QE by Yanis Varoufakis in The Global Minotaur, 2015, Zed Books, chapter 9, on why QE is not really money printing and why it cannot fuel inflation:
When the Fed buys $1,000 worth ofMBS paper from Bank X, $1,000 is taken out of the bank’s ‘assets’ column in the Bank X’s balance sheet and is replaced by $1,000 spending money held at a ‘reserve account Bank X keeps with the Fed. The said account’ is called ‘reserve’ because of the conditions the Fed attaches to its uses. To be precise, the Fed stipulates that this $1,000 can only be lent to other banks or used to buy other paper titles from other banks. Thus, the only way that the Fed’s purchase of this $1,000 ‘worth’ of MBS can find itself in the economy is if Bank X wants to buy some other piece of paper from another bank, say Bank Y. But even if it does, the money will enter the real economy only
if that piece of paper title is new – for example, if Bank Y had just lent $1,000 to some customer and passed this loan on to Bank X. If the paper title concerned is old, pre-QE. debt, all that QE would accomplish is that a paper title worth $1,000 would pass from the books of one bank to the books of another. The $1,000 would simply never enter the circular flow of income.