Puzzles, generally in verse, consisting of two words of equal length. The initial letters of the several lines constitute one of the secret words, and the final letters constitute the other word.
Also words re-arranged so as to make other words of similar significance, as “Horatio Nelson” re-arranged into Honor est a Nilo. Another form of acrostic is to find a sentence which reads the same backwards and forwards, as E.T.L.N.L.T.E., the initial letters of “Eat To Live, Never Live To Eat;” which in Latin would be, E.U.V.N.V.U.E. (Ede Ut Vivas, Ne Vivas Ut Edas).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Acrostics from Fact Monster: