'Rootstock' definitions:

Definition of 'rootstock'

(from WordNet)
noun
A horizontal plant stem with shoots above and roots below serving as a reproductive structure [syn: rhizome, rootstock, rootstalk]
noun
Root or part of a root used for plant propagation; especially that part of a grafted plant that supplies the roots

Definition of 'Rootstock'

From: GCIDE
  • Rootstock \Root"stock`\, n. (Bot.) A perennial underground stem, producing leafly stems or flower stems from year to year; a rhizome. [1913 Webster]