Question

the word which mean difficult to unravel or smooth out.

Answer 1

The word which means difficult to unravel or smooth out can be 'knotty'. There are many other words having similar meaning, for example 'intricate', 'tangled', 'complicated', etc. The word ‘knotty’ can be used in a sentence as: ‘This problem is quite knotty; unless you work very hard on it, you won’t be able to solve it.’ Another sentence that can be made is: ‘The situation is more intricate than you imagine; you must seek a specialist’s help.’

Answer 2

As Sudha Mam had written 

The words that mean 'difficult to unravel or smooth out' are- 
knotty
unyielding
perplexing
unfathomable
baffling

Hope this helps!