from Indian-embroidery definition:
It is a detached stitch that gives a raised effect. The needle is passed back through the fabric where the end of the bullion stitch is to end and again through to the front where the thread last came to the front. Before pulling out the needle, a coil of the thread is made on the needle that is of the same length as the stitch is required to be. The needle is now pulled through holding the coil thread in place with a finger. the needle is then pushed down at the same place it came out and marks the end of the knot.

This technique can be used as a mass effect laying bullion stitches along side each other to cover an area