unexplained
//ˌʌn.ɪkˈspleɪnd//
Adjective
unexplainedCanonical form
1
Not accounted for or made clear; lacking an explanation or reason.
The unexplained noise in the attic kept us awake all night.
2
Mysterious or puzzling due to the absence of a known cause or understanding.
The unexplained lights in the sky attracted many curious onlookers.