In hasan gharib, what dimension does gharib primarily indicate?

Hasan li-Dhatihi, Sahih li-Ghayrihi, and al-Tirmidhi’s Composite Terms

• A necessary condition that all routes be sahih or hasan
• Singularity or limited transmission routes at a relevant point
• Proof that every chain has deficient precision
• Proof that all routes share a disqualifying hidden defect