A best-manuscript edition is an edition based on the supposedly best manuscript, typically the earliest and/or best preserved manuscript in the tradition. For practical purposes, the term goes back to Joseph Bédier, who after struggling with the Old French Lai de l'Ombre for a number of years, drawing a number of conflicting stemmata, finally decided for a single, good manuscript. To determine which manuscript is "best" may be highly subjective.
For a fuller discussion, see the entries on codex optimus and editions, types of.
In other languages
DE: Ausgabe / Edition nach der besten Handschrift
FR: édition du meilleur manuscrit
IT: edizione, codice migliore / ottimo
OH