What is a grass slasher? A slasher is a heavy duty grass cutter, powered by a tractor. Usually used on grass that has not been cut for some time, although can be used for lawn mowing if needed.
Slashers are the best option for cutting extra long or tough grass. They can also cope with rugged or uneven ground which would otherwise quickly ruin a normal ride on mower. 
Using a tractor as it's power source, a slasher is capable of cutting large areas of long grass in a short amount of time.