subirrigation

noun

sub·​ir·​ri·​ga·​tion ˌsəb-ˌir-ə-ˈgā-shən 

: irrigation below the surface (as by a periodic rise of the water table or by a system of underground porous pipes)

subirrigate

ˌsəb-ˈir-ə-ˌgāt 

transitive verb

Word History

First Known Use

1835, in the meaning defined above