We don't have synonyms for upbow yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are up-bow, up bow and upblow.
(n) :
(music) A note performed on a string instrument by drawing the bow upward or to the left across the instrument, moving the point of contact from the bow's tip toward the frog.
(n) :
(music) A note performed on a string instrument by drawing the bow upward or to the left across the instrument, moving the point of contact from the bow's tip toward the frog.