n. A small book, usually made from a single sheet, folded several times, containing poems, ballads or religious tracts
the GNU version of the Collaborative International Dictionary of English
n. Any small book carried about for sale by chapmen or hawkers. Hence, any small book; a toy book.
The Century Dictionary and Cyclopedia
n. One of a class of tracts upon homely and miscellaneous subjects which at one time formed the chief popular literature of Great Britain and the American colonies.
Word Usage
"Tucked neatly at the back end of the chapbook is a selection of stills from the movie."