Daylighting can be defined as "opening up buried watercourses and restoring them to more natural conditions". An alternative definition refers to "the practice of removing streams from buried conditions and exposing them to the Earth's surface in order to directly or indirectly enhance the ecological, economic and/or socio-cultural well-being of a region and its inhabitants". The term is used to refer to the restoration of an originally open-air watercourse, which had at some point been diverted below ground, back into an above-ground channel. Typically, the rationale behind returning the riparian environment of a stream, wash, or river to a more natural state is to reduce runoff, create habitat for species in need of it, or improve an area's aesthetics. In the UK, the practice is also known as deculverting.

In addition to its use in urban design and planning the term also refers to the public process of advancing such projects. According to the Planning and Development Department of the City of Berkeley, "A general consensus has developed that protecting and restoring natural creeks' functions is achievable over time in an urban environment while recognizing the importance of property rights."