verb

• (intransitive, transitive) To remove the fleece from (a sheep, llama, etc.) by clipping.
  "shear the llamas"
• (physics) To deform because of forces pushing in opposite directions.
• (aviation, meteorology, intransitive, of wind) To change in direction or speed.
  "The total along-the-runway wind component sheared from an 8-knot headwind to about a 56-knot tailwind over a 44-second period."
• (mathematics) To transform by displacing every point in a direction parallel to some given line by a distance proportional to the point’s distance from the line.

noun

• (metalworking) A large machine use for cutting sheet metal.
• (physics) Forces that push in opposite directions.
• (aviation, meteorology, uncountable) The phenomenon of wind shear.
  "The first effect of a wind shear was detected at 34 to 42 seconds into the takeoff, at a speed of about 115 KIAS with the airplane about 3,800 feet down the runway. An average shear rate of about 2.5 knots per second resulted in an interruption in acceleration at this point with the airspeed remaining at 115 to 120 KIAS for 7 to 10 seconds."
• (aviation, meteorology, countable) A specific instance of wind shear.
  "We hit a nasty shear on approach and had to go around."