Noun

1. the act of circumscribing or the quality of being circumscribed
2. anything that circumscribes or a circumscribed area
3. the definition of what does and does not belong to a given taxon, from a particular taxonomic viewpoint or taxonomic system.

   The circumscription in the APG system of the family Malvaceae includes the former families Bombacaceae, Sterculiaceae and Tiliaceae.