Multicontextual refers to how something exists in many different settings or venues: physical, biological, cognitive, social, historical, etc. The multicontextual view of development is the understanding that people have many facets in their lives that intersect or overlap with each other. There are many contexts in which changes occur and different groups in which a person belongs.
For instance, as a child grows their lives may contain varying contexts of home, school, church, youth programs, and sports to name a few. While each of these venues is separate from the others they also overlap like a Venn diagram with each other and also with the life facets of other people making development and life multicontextual.