noun
miler (one-mile specialist)
Used in sports contexts for an athlete or horse that specializes in one-mile races.
彼は世界記録を持つマイラーだ。
He is a miler who holds the world record.
noun
mileage-run enthusiast; frequent-flyer point collector
Informal term for someone who actively accumulates airline miles, often through mileage runs.
He's a mileage-run enthusiast and flies abroad almost every month.