Tortious - Torturous - tortuous

The three words tortious, torturous and tortuous can give trouble, not least because the spellchecker will recognize them all as genuine English words and allow you to include them in an essay, even when they are wrong. Be clear.

• By far the most common (and most likely to be the one you want) is tortuous (pronounced 'TAUT-you-us', IPA: /ˈtɔː^rt ju əs/). This means 'twisting', 'winding' or 'full of twists ant turns.' This may be literal, as when Charles Darwin described the course of a river as 'tortuous', or other biologists call a tree's root 'tortuous'; it may also be figurative, as when the novelist Sterne applies the word to 'the ways of the human heart', meaning the emotions. There are often connotations of 'devious' or 'crooked', and it is not a compliment to describe a writer's style as tortuous, as when J.S.Mill said "The tortuous phraseology by which our author evades recognizing the ideas of truth and falsity".
• Tortious ('TAU(r)-shes', IPA: /ˈtɔː^rt ʃəs/) is a lawyer's word. It means 'to do with [the legal concept of] tort.' You are advised to avoid this word, unless you are a lawyer or law student. (OED includes, as meaning 4., " ¶4. Misused for TORTUOUS", which in itself is a warning.)
• Torturous does exist, but is rarely used correctly. Its correct meaning is 'to do with torture.' Student writers under the influence of the intrusive '-r-' have been known to write this when they mean tortuous. This is an error.

The word meaning 'twisting' is tortuous.
To spell this word Torturous is a mistake. 

Etymological note: The confusion between these words is understandable. They are all derived from the same root - the [Latin]] verb torqueo, torquēre, torsi, tortum, 'to twist'. Tortuous (from the past participle form tortus) is clear. To torture is to cause pain by twisting. (It is from this word that the second '-r-' in torturous is derived.) Tort ("English Law: The breach of a duty imposed by law, whereby some person acquires a right of action for damages" - OED) is derived from tortus too, in the sense that what is just is straightforward, and what is unjust is twisted, or crooked. Cf. the French phrase avoir tort, 'to be in error', 'to be wrong'. Other words from the same root include the verb 'to extort' (to squeeze [money] out of someone, as water is squeezed out of cloth); the related adjective extortionate; and the term used in Physics, engineering etc to name a twisting or rotary force: torsion.