Free Cash Flow (FCF) Quality is a value that gives you an idea of how stable the Free Cash Flow of a company is.
Linearity is calculated as standard deviation of the 12 LTM cash flow per share / average of the cash flow numbers
(the lower the ratio the better)
See also FCF Score, and FCF Growth.
the 'Free cash flow score' is according to Richard Tortoriello a predictive factor (especially in a combined screen with EV/EBITDA).