What was the rump parliament?

The Rump Parliament is the name of the English Parliament after Colonel Pride purged the Long Parliament on 6 December 1648 of those members hostile to the Grandees' intention to try King Charles I for high treason.

"Rump" normally means the hind end of an animal; its use meaning "remnant" was first recorded in the above context. Since 1649, the term "rump parliament" has been used to refer to any parliament left over from the actual legitimate parliament.

^ that's what you get from Wikipedia