Wiktionary
three-cornered jack
alt. 1 (context Australia English) The weed (taxlink Emex australis species noshow=1). 2 A seed vessel of this plant, which has three symmetrically arranged thorns and a pointed head. n. 1 (context Australia English) The weed (taxlink Emex australis species noshow=1). 2 A seed vessel of this plant, which has three symmetrically arranged thorns and a pointed head.