Plural of beltline; multiple highways or roads that encircle cities, or multiple horizontal lines marking belt positions on garments.
From 'beltline' plus the plural suffix '-s.' This is a standard pluralization of the compound noun.
Many major cities have multiple beltlines at different distances from downtown—Ring Road in London, the M25 outer belt, Interstate 610 in Houston. They're all trying to solve the same circular problem!
Complete word intelligence in one call. Free tier — 50 lookups/day.