Disbelief or uncertainty (about something); (countable) a particular instance of such disbelief or uncertainty.
To be undecided about; to lack confidence in; to disbelieve, to question.
A feeling of apprehension, doubt, fear etc.
A prick of the conscience; a moral scruple, a pang of guilt.
A sudden sickly feeling; queasiness.
To have a sickly feeling.