When in the lack of appropriate insults, to call one "booger" is to insult every part of the person including mind, body, and soul and to subject them to the ever taunting of the word. Whence calling someone "booger" the victim will show confusion before sudden realization of what they have been called, therefore falling into giggles before then going into depression. A very powerful insult indeed.
An annoying person that you can't get away from. Much like a booger, this person is very annoying and the only way to get rid of them is by wiping them off to someone else. The other person must now deal with this annoying booger.
"Here comes the booger"
"Man I can't stand this guy he won't go away!"