(set theory) The property of an orderedset such that its elements can be listed in an order such that, for every element, the element is irreducible (has exactly one upper or lower cover) in the subset consisting of that element and all subsequent elements.
(graph theory) The property of a graph such that its vertices can be listed in an order such that, for every vertex, the vertex is a subdominant vertex (has an adjacent vertex that is adjacent to every other vertex that it is adjacent to) in the induced subgraph generated by that vertex and all subsequent vertices.
