n. 1. Any of various coniferous evergreen trees or shrubs of the genus Thuja of North America and eastern Asia, having flattened branchlets with opposite, scalelike leaves and small cones. They are grown as ornamentals and for timber. Also called thuja.
2. Any similar plant of the related genera Platycladus or Thujopsis.
3. Anatomy The white nerve tissue of the cerebellum, which has a treelike outline in a median section.