An ambigram is a piece of writing that can be viewed in more than one orientation. Amazing things can be done with clever letter designs:
designed by (the other orientation is most easily viewed on a tablet computer or phone. Otherwise, you'll have to do a headstand to see it).
A natural ambigram is one where a word makes sense when viewed differently even without clever font design.
Sometimes the words might be the same when viewed upside down, as in the word dollop (well, more or less, apart from the l s being in slightly the wrong place). That example only works in lower case, but the word MOW, for example, works in both upper and lower cases. Then there are words like TOOTH, which stays the same if you write the word vertically:
and then put a mirror vertically down the middle of it (though why anyone should go to the trouble of doing that I do not know.)
A similar sort of thing happens if you put the mirror in horizontally in the word BOOK.
What's the use of ambigrams?
They're used in advertising sometimes, but they're just for fun, really.
But then that's important, isn't it.
Word To Use Today: ambigram. The claim is that this word was made up by the American professor of cognitive science Douglas Richard Hofstadter in about 1983, though the first known unnatural ambigram was made by Peter Newell in 1893. The Latin ambo means both, and -gram comes from the Greek gramma, which means letter.