doubting: marked by or given to doubt; "a skeptical attitude"; "a skeptical listener"
disbelieving: denying or questioning the tenets of especially a religion; "a skeptical approach to the nature of miracles"
(scepticism) agnosticism: the disbelief in any claims of ultimate knowledge
Contemporary skepticism (or scepticism) is loosely used to denote any questioning attitude, or some degree of doubt regarding claims that are elsewhere taken for granted.
(Scepticism (philosophy)) Philosophical skepticism (from Greek σκέψις - skepsis meaning "enquiry" - UK spelling, scepticism) is both a philosophical school of thought and a method that crosses disciplines and cultures. ...
Having, or expressing doubt; questioning; Of or relating to scepticism or the sceptics
(Scepticism) Scientific skepticism means that scientific claims must be exposed to critical scrutiny before being accepted.
(Scepticism) The view that nothing can be known with certainty; that at best, there can only be some private probable opinion. (PDP-502)