An acrostic is a poem or some other text written in an alphabetic script, in which the first letter of each verse, paragraph, or some other recurring feature in the text spells out another message.
Acrostics may simply spell out the letters of the alphabet in order; these acrostics occur in the Lamentations of Jeremiah, and in certain of the Psalms of the Hebrew Bible. Or, the acrostic may spell out a name or some other message, such as the acrostic contained in the Hypnerotomachia Poliphili, where the letters of the acrostic are embellished with ornate capital letters. Or, the acrostic may be used as a form of steganography, seeking to conceal the message rather than to proclaim it.