General:
* Hanging
* Suspending
* Swinging
* Drooping
* Loosening
* Precarious
More specific:
* Unattached (if referring to a lack of connection)
* Unsecured (if referring to something that could fall)
* Pending (if referring to something unresolved)
* Incomplete (if referring to a task or project)
* Unsolved (if referring to a mystery)
Figurative:
* Uncertain (if referring to a situation with an unknown outcome)
* Unsettled (if referring to a feeling of anxiety or unease)
* In limbo (if referring to something in a state of indefinite suspension)
To choose the best synonym, consider the meaning you want to convey and the context in which you are using the word.