Coupon Pass
The purchase of treasury notes or bonds from dealers, by the Federal Reserve.
Investopedia Commentary
The "coupon" refers to the coupons which are the main difference between T-notes and T-bills. The "pass" comes from when the Federal Reserve buys T-bills from dealers thus passing the bill.
Related Links
Money Market Tutorial
The Federal Reserve (the Fed) Tutorial
See also: Coupon, Treasury Bill, Treasury Bond, Treasury Note