CFM
Short for Cubic Feet per Minute, CFM sometimes abbreviated as CFPM is the air flow measurement used when describing how much air a fan or computer case fan is capable of distributing. The higher the CFM the more air the fan is capable of distributing, 70 CFM or more is a good starting value. When looking at the CFM it's also important to look at the fans dBA, smaller fans with a higher CFM will make more noise.
Also see: Case fan, Measurement, RPM