Green’s Dictionary of Slang

(Aus.) a penis.

1915		Sport (Adelaide) 26 Feb. 5/4: Elsie is the girl for a gardener’s wife, / Or that's what Kaiser Dick said, / And sport thinks she's a bonzer / In the good old parsnip bed.
1969		J. Hibberd Dimboola (2000) 78: bayonet: We all know what he concentrates on. mutton: Always points his great parsnip at the choirboys. aggie: Angus!