Quantitative tightening
Shrinking the central bank's balance sheet by letting securities mature without replacing them.
Quantitative tightening is usually passive. The Fed holds Treasury securities and mortgage-backed securities that mature on a schedule; rather than reinvesting the proceeds into new securities, it allows a set amount to roll off each month. The balance sheet shrinks without anything being sold.
That distinction matters for how it is reported. “The Fed is selling bonds” is generally not what is happening. Runoff caps set the maximum that is allowed to mature without reinvestment in a month, and the actual reduction can be smaller if less than that matures.
QT is how the Fed has unwound the holdings it accumulated through quantitative easing. It runs in the background of rate decisions rather than being announced meeting to meeting.