G'Day.....
Here in the Great White North we call them Brush Hogs... eh....
Like said. Brush Hog is a manufacturer and the term is used like the name Frigidaire is used for the appliance, refrigerator.
How ever I do agree the better term to use would be "slasher" because of the job they do on grass, weeds, brush.
There are a number of people in this area from OZ. And a few from Canada that have spent time "down under". It is fun comparing terms, like Loo from the Brits, Dunny, and Canadian term washroom.
The ways we are different and the ways we are the same. Interesting....