These units have some special means to disrupt their opponents in firefights.
For example, Noise Marines of Slaanesh use their psycho-sonic weapons to produce 'Kakophoni' effects that are both murderous and disorienting.
'CC Blast' and 'FF Blast' are temporary names — we hope to settle on better names for these abilities in future. In a perfect world, these abilities will have names that are evocative and yet which also neatly hint at the relatedness of their distinct yet similar gameplay effects. Easier said than done!
Where your detachment has the FF Blast ability and takes part in a firefight:
At the end of the FF3. Roll to resolve the firefight step, place one Blast marker on each enemy detachment that had any units within 15 cm of units in this detachment. This effect does not stack with other detachments that also have the FF Blast ability.