They say

> To get the cash, banks hand over Treasury notes and bonds, mortgages, and other securities, known as a “repo.” Then they get to borrow cash at face value.

Does that meet your standards?

It is a partial definition. To use the repo facility, borrowers don't just stake their assets, they also promise to re-buy them hours later at a higher price. It is literally overnight money issued in exchange for high-quality assets. If somehow the borrower goes broke within a few minutes, the Fed is still holding their assets.

Edit: I forgot about the haircut. The repo only lends out 98% of the staked assets value.