On Windows there is no easy way to clear the screen. On Linux and on Mac OS X typing CTRL-L will clear the screen.
:c and :clear will reset the terminal after a query fails with an error or is asking for more input and you want to abort the query.
Edited to add:
If the Gremlin console is in local mode (in other words you type :remote console to put it into local mode) you can do this:
gremlin> def cls() {
......1> for (a in 1..50) println " " }
then typing cls() will clear the screen
Edited again to add:
On more recent Windows 10 updates try this command in the Gremlin Console when in local mode.
println("\033[H\033[2J")
Or if your are already connected to the remote server try just entering the string on its own.
"\033H\033[2J\033[H"
