Bounded Context is a central pattern in Domain-Driven Design. In Bounded Context, everything related to the domain is visible within context internally but opaque to other bounded contexts. DDD deals with large models by dividing them into different Bounded Contexts and being explicit about their interrelationships.

Monolithic Conceptual Model Problem 

A single conceptual model for the entire organization is very tricky to deal with. The only benefit of such a unified model is that INTEGRATION is easy across the whole enterprise, but the drawbacks are many, for EXAMPLE:

1. At first, it's very hard to build a single model that works for the entire organization.
2. It's hard for others (teams) to understand it.
3. It's very DIFFICULT to change such a shared model to accommodate the new business requirements. The impact of such a change will be widespread across team boundaries.
4. Any large enterprise needs a model that is either very large or abstract.
5. Meaning of a single word may be different in different departments of an organization, so it may be really difficult to come up with a single unified model. Such a model, EVEN if created, will LEAD to a lot of confusion across the teams.