A stage in a mid-latitude depression where the cold front to the rear catches up with the leading warm front, lifts the wedge of warm air off the ground, and meets the cold air ahead of the warm front. If this overtaking air is colder than the cold air ahead of it, it will undercut it, forming a cold occlusion. If it is warmer than the cold air which is ahead of it, it will ride over it, in a warm occlusion. See B. Haurwitz (2007); see also Martin (1998) Month. Weather Revs 126, 2 and (1999) 127, 10; and Levizzani et al. (1989) Il nuovo cimento C 12, 2 (online), on a three-dimensional single radar analysis of an occluded front.
Power and Sidaway (2005) Soc. & Cult. Geog. 6, 6 use the term occluded geographies in describing Lisbon's Expo '98 to signify a reworking/re-presentation.