base level1
Physical Geography
noun
The lowest level to which a land surface can be eroded by running water.
- Sea level constitutes the continental or master base level; a local base level may be different from this..
Origin
Late 19th century.
base-level2
Physical Geography
verb
[with object] To reduce (an area, feature, etc.) to base level by erosion.
Origin
Late 19th century; earliest use found in Science.