Wikipedia
Buttress roots are large roots on all sides of a shallowly rooted tree. Typically, they are found in nutrient-poor rainforest soils and do not penetrate to deeper layers. They prevent the tree from falling over (hence the name buttress) while also gathering more nutrients. Buttresses are tension elements, being larger on the side away from the stress of asymmetrical canopies. The roots may interwind with buttress roots from other trees and create an intricate mesh, which may help support trees surrounding it. They can grow up to tall and spread for 30 metres above the soil then for another 30 metres below. When the roots spread horizontally, they are able to cover a wider area for collecting nutrients. They stay near the upper soil layer because all the main nutrients are found there.
Usage examples of "buttress root".
I followed the Fed, walking up the top of a buttress root like a steep ramp.
Golgotha is cut into a ridge of basalt that is flung out from the base of the mountain--like a buttress root from the trunk of a jungle tree--that separates the watersheds of the Yamamoto and Tojo Rivers.
He checked the loaded-chamber indicator on his submachine gun's receiver, switched the weapon off safe, and slipped three meters away from Tadziki to crouch in the gray folds of a buttress root.
Not that Cheerpt had any idea of what a buttress root was, and he had never seen a tall tree.
Luchare pulled Klootz's head around, and the two tugged him off behind the buttress root of a great tree, clearing the flimsy camp barrier as they did.
When he felt the mud under his boots begin to rise, he grasped a buttress root and stepped upward.
After a few minutes of very cautious progress in a semicircle, he stopped behind the enormous flying-buttress root of a giant tree.