The removal of forest and undergrowth
NSW-EPA, 1995

Refers to change of land cover with depletion of tree crown cover to less than 10%. Changes within the forest class (e.g. from closed to open forest) which negatively affect the stand or site and, in particular, lower the production capacity, are termed forest degradation
FAO, 1998

The conversion of forest to another land use or the long-term reduction of tree canopy cover below the 10% threshold
FAO, 2000

The direct human-induced conversion of forested land to non-forested land.
UNFCCC, 2001

Clearing of tree formations and their replacement by non forest land use
PEENRA website

A secondary forest that has lost, through human activities, the structure, function, species composition or productivity normally associated with a natural forest type expected on that site. Hence, a degraded forest delivers a reduced supply of goods and services from the given site and maintains only limited biological diversity. Biological diversity of degraded forests includes many non-tree components, which may dominate in the under canopy vegetation.
UNEP/CBD/SBSTTA, 2001

Forest that delivers a reduced supply of goods and services from a given site and maintains only limited biological diversity. It has lost the structure, function, species composition and /or productivity normally associated with the natural forest type expected at that site.
ITTO, 2002