rhi ‧ zome /ˈraɪzəʊm $ -zoʊm/ BrE AmE noun [countable]
[ Date: 1800-1900 ; Language: Modern Latin ; Origin: rhizoma , from Greek , 'mass of roots' , from rhiza 'root' ]
technical the thick stem of some plants, which lies under the ground and has roots and leaves growing out of it