Open Market Operations - OMO

What Does Open Market Operations - OMO Mean?
The buying and selling of government securities in the open market in order to expand or contract the amount of money in the banking system. Purchases inject money into the banking system and stimulate growth while sales of securities do the opposite.

Investopedia explains Open Market Operations - OMO
Open market operations are the principal tools of monetary policy. (The discount rate and reserve requirements are also used.) The U.S. Federal Reserve's goal in using this technique is to adjust the federal funds rate--the rate at which banks borrow reserves from each other.