What is mesostic?

A mesostic is a poem or other composition in which a vertical phrase intersects lines of horizontal text. The vertical phrase is usually a name or a word, with the letters of that word appearing at equal intervals in each line of the composition. Mesostic is a form of acrostic poetry, which uses the initial or final letters of each line to spell out a message. Mesostics were popularized by the American composer John Cage, who used them extensively in his musical compositions and poetry. The use of mesostics creates a unique and often unpredictable structure to the composition, while also highlighting a particular word or theme.