The act of using a corner of a desk or any inanimate object to stimulate one's clitoris. The person grevstabating will try to make it look as though they are not grevstabating but anyone who is aware of grevstabation will catch on quite quickly.
" Oh sick, my teacher was totally Grevstabating all over my desk it was so obvious"
"Really I didn't know she liked to grevstabate"