ungewiss
uncertain
A state or future that is not known, secure, or predictable. It describes a situation full of uncertainty.
Ob er die Prüfung bestanden hat, ist noch ungewiss.
Whether he passed the exam is still uncertain.

uncertain / hesitant
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uncertain
A state or future that is not known, secure, or predictable. It describes a situation full of uncertainty.
Ob er die Prüfung bestanden hat, ist noch ungewiss.
Whether he passed the exam is still uncertain.

The prefix 'un-' expresses negation. 'Ungewiss' (uncertain) is the opposite of 'gewiss', which means 'certain'. So 'ungewiss' means 'not certain'.
Die genaue Ursache des Problems ist noch ungewiss.
The exact cause of the problem is still uncertain.
In the meaning 'uncertain', 'ungewiss' is often used in the fixed structure 'Es ist ungewiss, ob ...' (It is uncertain whether ...), followed by a subordinate clause.
Es ist ungewiss, ob das Wetter morgen gut genug für die Wanderung sein wird.
It is uncertain whether the weather will be good enough for the hike tomorrow.
You can recognize the meaning from the usage: if 'ungewiss' refers to a situation or the future, it means 'uncertain'. If it describes a person or their movements, it means 'hesitant'.
Der Ausgang der Wahl ist noch völlig ungewiss.
The outcome of the election is still completely uncertain.
When 'ungewiss' describes a person, it often comes before nouns like 'Schritte' (steps), 'Blick' (look), or 'Stimme' (voice) to express uncertainty in behavior.
Mit ungewisser Stimme fragte sie, was passiert sei.
In a hesitant voice, she asked what had happened.
sure / safe
'sicher' and 'ungewiss' are opposites when it comes to knowledge, planning, or the future. 'sicher' means that you have no doubt or that something is settled. 'ungewiss' means that you do not yet know how something will turn out or what will happen. So 'sicher' fits clear information and firm decisions. 'ungewiss' fits open situations in which many things are still possible.

Nach der Kündigung war ihre Zukunft bei der Firma ungewiss.
After the dismissal, her future at the company was uncertain.
Im Bus ist schon sicher, dass die Besprechung morgen stattfindet.
On the bus, it is already certain that the meeting will take place tomorrow.