In † singular and plural With the: a range of low hills skirting the western slopes of the Apennines in Italy.
Of or relating to this range of hills or (Geology, now chiefly historical) the Pliocene strata which are exposed there. Also more widely: designating the region adjacent to the Apennines; of or relating to this region.
Early 19th century; earliest use found in James Smith (1775–1839), writer and humorist. From sub- + Apennine, after Italian subappennini, †subapennini.