something left behind by small orphans when they try to pick your pockets and find no money, they leave this behind so that there may be evidence of their existence as they are not normally noticed by people as no one cares about them.
omg i found pocket lint in my pocket a orphan must have visted my pocket
a person/friend that will provide you with sexual favors at the drop of a hat.
At a bar...trying to pick up women. You notice that "pocket lint" is there. You try to pick up other women in the meantime, and if you are unsuccessful, old reliable "pocket lint" is there ready to go home with you.