Can you think of a word in the English language that, when written, can be turned upside-down to result in an abbreviation of the antonym of the original word?
Where "turned upside down" is a 180 degree rotation about a central point. (i.e. "moo" would become "oow")
The word up written in small letters. The word "up" turned upside down is "dn" which is the abbreviation for down, and "up" is opposite in meaning to "down".