A site, to be used for housing or commerce, whose previous use (if any) was agricultural
"The city council approved plans to convert the abandoned farmland into a new commercial district."
Being a completely new development, without the need to integrate with legacy systems etc.
"The startup chose a greenfield approach for their cloud migration, allowing them to build entirely from scratch without worrying about patching up decades-old on-premise servers."
A surname.
"The new CEO, a Mr. Greenfield, announced his plans during the quarterly meeting."