fisherman's knot

noun

a knot for joining two ropes of equal thickness consisting of an overhand knot or double overhand knot by each rope round the other, so that the two knots jam when pulled tight

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012