DCHP-1 Online
rock elm 
a tree, Ulmus thomasi, of eastern Canada; also, the tough wood of this tree.
- 1830 The timber of this variety . . . is known by the name of Rock Elm.
- 1952 Rare species in the upper St. Lawrence are basswood and rock elm.
- 1955 Southern Ontario . . . is sending . . . rock elm timbers to Britain. . . .
- 1830 The timber of this variety . . . is known by the name of Rock Elm.