Defined Terms and Documents Discussion Paper Annexure A Annexure B
Greenfield means a new piece of infrastructure ie. power plant, airport, gas pipeline, Telco, new train network etc which are built from scratch on what is essentially a green field, albeit it could be underwater ie. the JV of Transfield and Kumagai built the Sydney Harbour Tunnel over 20 years ago.
See also Brownfield, Thirteen Steps To Complete A Greenfield Or Brownfield Infrastructure Project Finance.