COLLOCATIONS FROM OTHER ENTRIES►a thorny/knotty problem
(=difficult)· He still faced the thorny problem of finding a way out of the jungle.
COLLOCATIONS FROM THE CORPUSNOUN►problem
· I have had many letters from knitters asking for help with knotty problems.· Flying is at the heart of this knotty problem.· And in fact patient research has gone a long way towards resolving this knotty problem.· Night after night, all over the country, ordinary married couples must be wrestling with exactly this sort of knotty problem.
1difficult to solve: a knotty problem2knotty wood contains a lot of hard round places where branches once joined the tree