FWIW:
FAA H-8083-16B: Approaches whose final approach segment is more than 30 degrees different from the landing runway alignment are always designated as circling approaches.
.
E.g.: When the landing is to be made on a runway that is not
aligned with the approach being flown, the controller may
issue a circling approach clearance, such as “…cleared
for VOR Runway 17 approach, circle to land Runway 23.”
EASA: A circling approach is the visual phase of an instrument approach to bring an aircraft into position for landing on a runway which is not suitably located for a straight-in approach. (JAR-OPS 1.435 (a) (1))
JEPPESEN: CIRCLING APPROACH / CIRCLE-TO-LAND MANEUVER — An extension of an instrument approach procedure which provides for visual circling of the aerodrome prior to landing.
