The phrase "idle cash" refers to money that is not being used or invested. It is simply sitting there without any purpose or being utilized for any activities. Full definition
Banks don't hold stack a pile of idle cash in a corner of the vault to maintain these reserves. (hussmanfunds.com)
Link your checking account to a variety of investment fund options to generate returns on idle cash balances. (pnc.com)
Before heading off on my three week vacation, I decided to make a couple buys to decrease the amount of idle cash in my portfolio. (dividendsinhand.com)