This is on the top of the WSJ
The idea of the bond buying program being “sterilized” means that in addition to buying bonds, the Fed would also be selling assets (theoretically).
From the article:
Under the new approach, the Fed would print new money to buy long-term mortgage or Treasury bonds but effectively tie up that money by borrowing it back for short periods at low rates. The aim of such an approach would be to relieve anxieties that money printing could fuel inflation later, a fear widely expressed by critics of the Fed’s previous efforts to aid the recovery.
Basically, it sounds like operation twist.
The article goes onto stress that there’s no decision that’s been made up, and that this might never happen.