1 [not before noun]
feeling doubt about something [= unsure]
uncertain whether/how/what etc
He was uncertain how much further he could walk.
I was uncertain about what to do next.
not clear, definite, or decided [= unclear]
It is uncertain whether/how/what etc
It is uncertain how likely this is to occur.
My whole future now seemed uncertain.
if you tell someone something in no uncertain terms, you tell them very clearly without trying to be polite:
I told Colin in no uncertain terms what I thought of him.
if someone walks in an uncertain way, they seem as though they might fall:
She took a few uncertain steps forward.