(In certain plants, especially trees such as mangroves) an adventitious root that grows out from the lower part of the stem or lower branches, serving to give it additional support.
Origin
Mid 19th century.
Definition of prop root in US English:
prop root
noun
(In certain plants, especially trees such as mangroves) an adventitious root that grows out from the lower part of the stem or lower branches, serving to give it additional support.