Thorn

1. A sharp protective spine of a plant.
2. Any shrub or small tree that bears thorns, especially a hawthorn.

   the cockspur thorn

3. That which pricks or annoys; anything troublesome.
4. A letter of Latin script (capital: Þ, small: þ), borrowed from the futhark; today used only in Icelandic to represent the voiceless dental fricative, but originally used in several early Germanic scripts, including Old English where it represented the dental fricatives that are today written th (Old English did not have phonemic voicing distinctions for fricatives).

verb

To pierce with, or as if with, a thorn