A shear is a cutting implement that looks like a long pair of scissors. Also like scissors, this form of the noun is usually plural. You can cut metal, prune a tree, or cut up a chicken with shears.
In farming, when you remove wool from a sheep, goat, or even a llama, you shear the animal. Most farmers shear their sheep once a year, but the timing varies from farm to farm. The verb shear also means to cause to break off or come apart with a cutting force. The wind during a storm can blow hard enough to shear the tiles off a roof.