rot13

rot13 /rot ther'teen/ /n.,v./ [Usenet: from `rotate alphabet 13 places'] The simple Caesar-cypher encryption that replaces each English letter with the one 13 places forward or back along the alphabet, so that "The butler did it!" becomes "Gur ohgyre qvq vg!" … It is used to enclose the text in a sealed wrapper that the reader must choose to open — e.g., for posting things that might offend some readers, or spoilers. …