The correct spelling for this word is in fact 'treacherous'. It is pronounced tre-cher-rous so is spelled in a similar way. The word has quite a few different meanings and can be used in many contexts.  It can mean dangerous, for example 'the treacherous road lay ahead', or also a deliberate betrayal: 'his treacherous behaviour shocked her'. It can also be used to describe something or someone who shouldn't be relied or depended on: 'beware of them - they're treacherous people'. It is linked to the word 'treason' which is a betrayal of your country - 'he was imprisoned for his treason'. Other forms of the word are 'treachery' - 'the treachery stunned us'; as well as the lesser used 'treacherousness' - 'she couldn't help noticing the treacherousness of the waters', and 'treacherously' - 'treacherously, he made his way up the mountain'. The word isn't used so much nowadays but it is by no means old-fashioned.