I have a friend who has several tattoos. She calls them sleeves. 
There is actually a difference between a sleeve and an arm covered in tattoos.
Really? What is the difference?
A sleeve tattoo has a unified theme where as someone with a bunch of different arm tattoos doesn't quailify techincally.
Who decides what is and isn't a sleeve though?
If they are different styles and themes from each other it isnt a sleeve. A sleeve goes together not a bunch of random things.
What else do you know about sleeve tattoos?
Well as expected it gets its name from its likening to a long sleeve shirt.
That makes a lot of sense. I bet it is really expensive to get those kinds of tattoos...
below the elbow. A sleeve implies complete tattoo coverage of a particular area, so a half sleeve is a tattoo that covers the entire upper or lower arm. A "quarter sleeve" usually covers the area of skin from the shoulder midway to the elbow.
Sleeve tattoos are a collaboration between a tattoo artist and customer to demonstrate a personal and unified artistic theme. Other times, a sleeve is created when a person has many smaller tattoos on their arm and later has them connected with background tattooing to form a sleeve
Sleeve tattoo
A sleeve tattoo (or tattoo sleeve) is a large tattoo, or a collection of smaller tattoos, that has a unified theme, that covers most or all of a person's arm, usually from shoulder to wrist.
There is a difference between an arm covered in tattoos and a sleeve tattoo. A sleeve tattoo has a unified theme, whereas an arm covered in tattoos may have many tattoos of different styles that does not have an overall unity.
The term "sleeve" is a reference