What it means
You say boonies when you're talking about a place that's so far off the map your GPS starts weeping. It's the heart of nowhere, where the wild things yawn and the nearest corner shop is a daydream. People use it when they're lost in the sticks or describing somewhere delightfully removed from the pulse of the world.
Usage examples
"Mate, I've been driving for an hour and I'm still in the boonies. Not even a petrol station in sight."
"Her new place is cute but it's deep in the boonies. Pack a sandwich for the trip to grab milk."
"We used to mess around out in the boonies as kids, building forts and dodging raccoons."