three-cornered jack

noun2

1. •
   (Australia) A weed of species Emex australis.

   • The “Three-cornered jack/Devils thorn” (Emex australis) is believed to be poisonous to them, as many dead locusts are found near to each plant. — 1901
2. •
   A seed vessel of this plant, which has three symmetrically arranged thorns and a pointed head.