sceptical

• He had found himself startled, sceptical, and now a good deal disturbed. —  Vanishing Point - Patricia Wentworth - Miss Silver 24: 1953
• "I'm pretty sceptical, and usually there's a rational explanation, but it could be that someone out there is sitting on something really interesting." —  Latest News Breaking News and Current News from the UK and World Telegraph
• At first they were a little sceptical, apparently the screens either work or not. —  MoDaCo WinMo News
• She respects the opinions of those who are sceptical, and says there are charlatans out there in just the same way that there are dodgy builders. —  Shropshire Star
• My companion, whom I took at first to be a rather ironic, sceptical, and by nature "unimaginative globe-trotter--he was a hard-looking, iron-grey man of middle-age--related the usual tiger story, the time-honoured elephant anecdote, and a couple of snake yarns of no special value, and I was beginning to fear that I should get little entertainment from so prosaic a sportsman, when I chanced to mention the desert Ah!" —  The Figure In The Mirage 1905

Roget's II: The New Thesaurus

Used in the Same Context