Definition of chain stitch:
(n) :
(machine sewing) A stitch in which the looping of the thread or threads forms a chain on the underside of the work; the loop stitch, as distinguished from the lock stitch.
(n) :
An ornamental stitch like the links of a chain, used in sewing and embroidery.
(n) :
A stitch like the links of a chain, used in crocheting.