reef knot 
noun chiefly British
A type of double knot which is made symmetrically to hold securely and cast off easily.But it's very, very hard to criticise someone when your windpipe is in a reef knot from concussive laughter....
- Randhawa, 32, a placid sort of fellow who attributes his temperate nature to yoga, did not feel the need to adopt the lotus position once, probably on the grounds that it is difficult to hit a golf ball when your legs are tied in a reef knot.
- His style, drier than toast and tighter than a reef knot, works best in shorter bursts but - except for the occasional mawkish diversion - his new book is hugely enjoyable.