"Please Fuck Off Letter" - (pronounced "pee-fall") - A very politely worded rejection letter. It can be used in any context where one's application (for employment, to be published, etc.) is rejected. Such letters can also, through their precise politeness or use of wording, imply not only that you are rejected, but that you deserve to be rejected because you do not, in their opinion, measure up to their self-perceived standards.
Q: "Did the firm of Booth, Cream & Crippen accept your application to be a summer student?"
A: "Nah, I just got the PFOL today."