according to the online bible of investing
Liquidity describes the degree to which an asset or security can be quickly bought or sold in the market without affecting the asset's price.
https://www.investopedia.com/terms/l/liquidity.asp
A liquid asset is an asset that can be converted into cash quickly, with minimal impact to the price received in the open market.
https://www.investopedia.com/terms/l/liquidasset.asp
in steem terminology its the steem you havent used to power up that's sitting in your wallet doing nothing, like the money in your pocket
that's liquid
you'll have to excuse me if i dont spend six hours on it today i got stuff to fix in my scripts :)