unknown caller 

1. someone who is too scared to show who they are and hide caller id, and phone then hang up.
2. when they realise they have phoned the wrong number, they're too embarassed to mention it, and leave you hanging, .. repeating "hello" over and over again, until you give up and feel annoyed at the phone.
3. someone who phones, but is too rude to say who they are, and leave a long message then hang up before giving their name.

1. *ring ring*
..who is it?... unknown caller.. hmm
*pick up phone*
"hello?.. hello?"
*hang up*

unknown caller by sam was here June 16, 2008