Vorpal is a word (almost invariably an adjective) coined by
Lewis Carroll for the poem "Jabberwocky," used first in the
line "He took his vorpal sword in hand" and "One, two! One,
two! And through and through / The vorpal blade went
snicker-snack! / He left it dead, and with its head / He went
galumphing back." Vorpal is commonly assumed to mean
"deadly" or "sharp", and may imply that the blade has magical
properties. Many role-playing games (beginning with
Dungeons & Dragons) have taken the latter interpretation
and, since the hero brings the dead Jabberwock's head
home in triumph, have used "vorpal" to identify weapons
with a magically enhanced ability to behead enemies. It is
also occasionally interpreted as meaning the blade is warped

                   
Vorpal at wikipedia.
What is a Vorpal?