In the US, a straight-in procedure is one aligned within 30 degrees of the runway, and beyond that only circling minimums are published. I believe ICAO follows the same guideline. (ICAO states not more than 30 degrees between runway centerline and final approach course alignment for category A and B aircraft, and I believe 15 degrees for all other aircraft, with not less than 900 meters between the point of intersection of the approach track and runway centerline). Lack of straight in minimums doesn't preclude a landing straight in if one is able to see the runway in time to maneuver normally and align one's self with the runway (depending on specific procedure restrictions).
The term straight-in approach is also used in conjunction with procedures not requiring course reversal such as a procedure turn.