Meaning of abyssal plain in English:
abyssal plain
noun
OceanographyAn extensive level area of the deep ocean floor, typically situated between the foot of the continental rise and an oceanic trench and covered with a smooth layer of sediment.
Origin
Late 19th century; earliest use found in Thomas Huxley (1825–1895), biologist and science educationist.
Are You Learning English? Here Are Our Top English Tips