Distrustful is an adjective for a person — or a look, a mood, a public — who cannot easily trust. Underneath is the feeling that you are not safe with someone, or that you cannot believe what they say, and the word puts that feeling on someone as a quality. A distrustful student checks the story twice. A distrustful customer reads the small print. You are usually distrustful of a person or of a thing: that of matters. It is reasonably ordinary English, a little more careful than “suspicious,” and a little less like crime. Though actually, it is not the same as “careful.” Careful people still trust, but they watch. Distrustful people have already leaned toward no. And it does not mean you are untrustworthy — that would be about whether others can trust you. Distrustful is about whether you can trust them. People use it for a passing mood (“He sounded distrustful”) and for a longer habit of mind.