The process is called shearing, or clipping.
Shearing
shearing
Chickens are plucked. Though this is true without first sheering a sheep. :)
clean it
Sheep grow wool. When the wool is shorn from a sheep it is called a fleece.
A fleece is what the wool is called when it is shorn from a sheep.
wool
Wool.
Wool
Once a year, in the spring, a shearer uses hand shears (similar to large scissors) or electric shears (similar to an electric razor) to cut the wool off the sheep. The sheep don't mind the process, and as soon as the weather warms up they're really glad to be rid of all that wool!
More properly, the raw material from which wool is spun is called fleece.
Sheep grow wool and when it is shorn from the sheep it is called a fleece.