spirit level spirit level /ˈspɪrɪt ˈlɛvəl/

noun

1. Indicator that establishes the horizontal when a bubble is centered in a tube of liquid  ( spirit level , level )
   indicator that establishes the horizontal when a bubble is centered in a tube of liquid
    He used a spirit level to check if the surface was even
   He used a spirit level to check if the surface was even