We don't have synonyms for stably yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are stable, starly and stabby.
(n) :
(hunting, historical) A medieval hunting practice in which a group of hunters and hounds are stationed around the perimeter of a wood during a hunt to prevent the escape of the game.
(n) :
(hunting, historical) A medieval hunting practice in which a group of hunters and hounds are stationed around the perimeter of a wood during a hunt to prevent the escape of the game.