barre also
bar 
(bär)
n.1. A handrail fixed to a wall, as in a dance studio, used by ballet dancers as a support in certain exercises.
2. A fingering technique used with fretted stringed instruments in which a finger is laid across the fretboard to stop all or several strings at once.
[French, from Old French, from Vulgar Latin *barra, of Gaulish origin.]