STRAIGHT-IN APPROACH IFR
An instrument approach wherein final approach is begun without first having executed a procedure turn, not necessarily completed with a straight-in landing or made to straight-in landing minimums. That's AIM.
1.2.3 Types of approach
1.2.3.1 There are two types of approach: straight-in and circling.
1.2.3.2 Straight-in approach
Whenever possible, a straight-in approach will be specified which is aligned with the runway centre line. In the case of non-precision approaches, a straight-in approach is considered acceptable if the angle between the final approach track and the runway centre line is 30˚ or less.
1.2.3.3 Circling approach
A circling approach will be specified in those cases where terrain or other constraints cause the final approach track alignment or descent gradient to fall outside the criteria for a straight-in approach. The final approach track of a circling approach procedure is in most cases aligned to pass over some portion of the usable landing surface of the aerodrome.
That's ICAO.
