Leather is a flavor description, not a type of wrapper. People use it when the smoke tastes tannic, dry and slightly sweet, or reminds them of a leather belt or chair, in the same way they use “cedar” for the smell of a cigar box. It is often used for dark wrappers and some sun-grown habano wrappers, but that is not a rule.
Smoke Rings uses the word in its ordinary meaning, not as part of a formal tasting system. If we cannot describe a flavor plainly, we do not include it.
See earth and cocoa for the two other tasting terms in this glossary, and the reviews for descriptions of individual cigars.