You searched for: “ventometer
ventometer (s) (noun), pentameters (pl)
A device for displaying the velocity of the wind: A ventometer is tool for making micrometer adjustments to the sight of a rifle so as to make modifications in windage (horizontal adjustment that moves the barrel to adjust for left to right sighting) and elevation (vertical adjustment) by turning the ventometer to the adjustments necessary for greater accuracy when shooting at a target.