Any of several North American elms, especially the cork elm, Ulmus thomasii, of the Midwest and parts of Canada; (also) the hard heavy timber of this tree, formerly much used for shipbuilding.
Origin
Early 19th century.
Definition of rock elm in US English:
rock elm
noun
Any of several North American elms, especially the cork elm, Ulmus thomasii, of the Midwest and parts of Canada; (also) the hard heavy timber of this tree, formerly much used for shipbuilding.