a set of varied, irregularly shaped pieces that, when properly assembled, forms a picture or map; named because picture, originally attached to wood and later to paperboard, was cut into its pieces with a jigsaw; range in difficulty by factors such as number of pieces; originated as educational devices (dissected maps) to teach geography in 18th-c. England; use of popular pictures began in 1860s and 1870s, in Great Britain and U.S.; extremely popular in early 1900s and had revival in Great Depression of 1930s as inexpensive, reusable amusement.