Loosely coupled architecture refers to a system where components interact with minimal dependence on each other, enabling changes in one without affecting others.

Its impact is profound, fostering flexibility, efficiency, and resilience in development, testing, and maintenance. This minimizes risks and costs, allowing for a more agile response to market needs. It might imply techniques like single responsibility, microservices, and event-driven designs.

A loosely coupled architecture is pivotal in building scalable and adaptable systems. It promotes better collaboration between teams, faster development, easier testing, and it facilitates the introduction of new technologies or changes without affecting the whole system. But, if the architecture is tightly coupled, changes in one part can lead to a domino effect requiring changes elsewhere. This makes maintenance difficult, increases the likelihood of bugs, slows down the development process, and can make onboarding new team members more challenging.