Tenuous is an adjective with a few meanings:
- thin or slender in form, as a thread.
- lacking a sound basis, as reasoning; unsubstantiated; weak
- thin in consistency; rare or rarefied.
- of slight importance or significance; unsubstantial
- lacking in clarity; vague
It comes from the Latin word tenius, meaning thin. I’m guessing that all the other meanings developed later – and it’s interesting how they’re all more or less related. A search for “tenuous” on Google News shows many different uses, like “Oil Market Reaches Tenuous Balance”, “a tenuous grip on reality”, “tenuous reasoning”, and even a “tenuous nose injury”, whatever that means.