A material of short fiber and inferior quality obtained by deviling woolen rags or the remnants of woolen goods, specif. those of felted, milled, or hard-spun woolen cloth, as distinguished from shoddy, or the deviled product of loose-textured woolen goods or worsted, -- a distinction often disregarded.
[Webster 1913 Suppl.]
Note: Mungo properly signifies the disintegrated rags of woolen cloth, as distinguished from those of worsted, which form shoddy. The distinction is very commonly disregarded. Beck (Draper's Dict.).