Originally Posted by IainMurray
to splice is to open the lay of a rope and re-weave it to create a ring / hoop / bight at one end or lay it back onto itself in a "long splice" to stop it unravelling. You can also join two identical rope together neatly.
When you lay the rope back on itself to stop unravelling, it's a back splice. The long splice is the joining of two identical ropes together in such a fashion that the diameter is only marginally increased, so it will still run through a block.