noun

• (Australia, Canada, New Zealand, US) A yard to the rear of a house or similar residence.
  "I think when I discovered this republic, which is in Nevada - in one man's house and backyard and front garden - I think I stumbled across what for me really typifies the whole micronational movement."
• (Australia, Canada, New Zealand, US, colloquial) A person's neighborhood, or an area nearby to a person's usual residence or place of work and where the person is likely to go.
  "The entire beach was my backyard, from the Hiltons' house in the south all the way to Steele Hunter's house in the north."
• (Australia, Canada, New Zealand, US, colloquial) An area nearby to a country or other jurisdiction's legal boundaries, particularly an area in which the country feels it has an interest.
  "However, the region was in the United States backyard and Britain should look passively on with acquiescence in whatever policy the United States saw fit to pursue about Mexico."