What is the meaning of Thistle?

Any of several perennial composite plants, especially of genera Cirsium, Carduus, Cynara, or Onopordum, having prickly leaves and showy flower heads with prickly bracts.

This plant seen as the national emblem of Scotland.

This plant used as a charge.

The Order of the Thistle, or membership thereof.

Source: wiktionary.org