A shearer is a person whose job is to cut the wool off a sheep, close to the skin, with special shears or a powered handpiece. The work is fast, skilled, and hard on the back. You hear the word most in places with big sheep farms — Australia and New Zealand especially, where shearing is a real trade and teams travel from farm to farm. In a story or a film about wool, this is the worker you meet. It is a job name, not a casual nickname, and it is not a hairdresser: human hair is a different job. It also does not usually mean someone who cuts metal in a factory. From the verb shear (to cut wool) plus -er, the person who does it.