A sleeve tattoo covers most or all of a person's arm. Do you know anyone with a sleeve?
I use to know someone with a sleeve tattoo. It was entirely Pearl Jam-themed. But I haven't talked to him in years. 
Apparently they also use this term to refer to a large leg tattoo - but I've never personally heard it called that.
A leg sleeve? I've never heard of that either. I've got a few tattoos myself. Someday I'd like a half sleeve, but probably not the whole thing. On my arm, of course, not my leg. 
Yep a leg sleeve LOL!  You could get a quarter sleeve that only covers part of the arm 
That's probably what I'd want. Do you have any tattoos? 
I actually don't but it has more to do with the pain of it than anything else.  I mean inserting the ink into the dermis layer of the skin with multiple needles?  
The needles are definitely a valid concern. If I remember correctly, it was a different setup for doing black lines versus shading and color. Do you know anything about the inks composition?
Process of tattooing
The process or technique of tattooing, creating a tattoo, involves the insertion of pigment into the skin's dermis. Traditionally, tattooing often involved rubbing pigment into cuts. Modern tattooing almost always requires the use of a tattoo machine and often procedures and accessories to reduce the risk to human health.
Physiological process of tattooing.
Tattooing involves the placement of pigment into the skin's dermis, the layer of dermal tissue underlying the epidermis. After initial injection, pigment is dispersed throughout a homogenized damaged layer
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