1. (noun) a wilderness at the edge of a settled area of a country

• wild
• wilderness

2. (noun) an international boundary or the area (often fortified) immediately inside the boundary

• bound
• boundary
• bounds

3. (noun) an undeveloped field of study; a topic inviting research and development

• bailiwick
• discipline
• field
• field of study
• study
• subject
• subject area
• subject field