ambigram

From ambi- +‎ -gram. Coined by Douglas Hofstadter.[1]

ambigram (plural ambigrams)

1. A calligraphic design that may be read as the same word or phrase (or sometimes different words or phrases) when oriented in two different ways, usually when reflected along a vertical or horizontal axis or when rotated through 180 degrees.
   • 1992, John Langdon, Wordplay, published 2005, page 52:

     Two nonvisual factors provide dissymmetry and prevent the ambigram from existing in a static equilibrium; most of the letters in an ambigram metamorphose into other letters when reversed; and each of those accompanying sentences provides a different idea of the word's meaning.

   • 1997, Research and Education Networking, Volume 8, Issues 1-6, page 290,

     An ambigram is a word that reads the same right-side-up and upside-down. MOW is a natural ambigram, for instance, but any word can be flipped if the right graphic artist gets his hands on it.

   • 2007, Douglas Hofstadter, I Am a Strange Loop‎, page 312:

     Next, I imagine that Switch #2 causes me every single weekend (and every other spare moment as well) to elect, instead of designing ambigrams or working hard on my book about being a strange loop, to spend hours on end watching professional football games on a huge-screen television and delightedly ogling all the busty babes in the beer ads.