Stum Edit Meaning

1.

To not talk. To "stay stum".

As far as I can tell it derives from 19th century England/Australia, as read in Bryce Courtenay's 'The Potato Factory'

Hey thanks for staying stum about my involvement in that bank heist..

See quiet, dumb, zip it

2.

Someone that hangs out in Starbucks all the time like they haven't got a regular home. A 'Starbuck's bum'.

Man, I wish that stum would stop hogging the power socket by the wall over there!