He got super defensive the moment another manager tried to make decisions on his turf.
The speaker is describing someone who feels threatened when someone else interferes in their area of authority.
Noun phrase: the turf
Vibe: Territory and authority
Someone's personal territory, home area, or domain where they feel in charge and protective.
Watch out, you're stepping onto rival turf.
You picture a neighborhood cat sitting proudly on a wooden fence, staring down any outside animal that dares to walk into its yard.
Real-life examples
We are playing on their home turf tonight, so expect a tough crowd.
The speaker is explaining that the game is in the opposing team's stadium, giving them the emotional upper hand.
Synonyms
Contrast & nuance
Unlike 'territory,' which is a neutral word for an area, 'turf' implies aggressive ownership and control. While 'stomping ground' simply means a place you visit often, 'turf' is a place you actively claim and protect from intruders.