n. In botany:n. A rootlet: same as radicel.n. Specifically, same as caulicle: by late writers appropriately restricted to the rudimentary root at the lower extremity of the caulicle.n. In anatomy and zoology, a little root or root-like part; a radix: as, the radicles of a vein (the minute vessels which unite to form a vein); the radicle of a nerve.n. In philology, same as radical, 1.n. In chem., same as radical, 2.n. In the graptolites, the proximal extension of the virgula.