rock elm

1. A deciduous eastern North American tree (Ulmus thomasii) having corky branches and coarsely toothed leaves.
2. The wood of this tree.

The noun has 2 meanings:

Meaning #1: tall widely distributed elm of eastern North America
  Synonym: Ulmus thomasii

Meaning #2: large ornamental tree with graceful gradually spreading branches common in eastern North America
  Synonyms: American elm, white elm, water elm, Ulmus americana