a sarcastic remark when you ask somebody to do something for you when you need a favor and they are too busy or to stupid to realize you are really needing their help. Stating that THEIR problems are far more important than yours and don't want to be inconvenienced.
For example, let's say you are filling out an application somewhere and you need a pen and you ask one of the clerks to barrow a pen and they reply back "Sorry, i don't wear pins" - "STBY...."
"Hey mom, i need to be dropped off at school early, do you care to take me to school about 15 minutes early?"
and she responds "No, i have to walk the dog during that time." "..... STBY"