mash on (something)
To press down on something very forcefully and without finesse. Don't just start mashing on the keyboard when the computer stalls like that—you'll only make it freeze up even worse. I've got a patient who's been mashing on the call button every 10 minutes.
mash on something
to press on something, such as a button. (Southern.) He kept mashing on the doorbell until someone responded. Just mash on this button if you want someone to come.