In a row; one after another in a line or sequence.
From Middle English 'arwe' or 'a rewe,' combining the preposition 'a' (on) with 'row' (a line). This is an older, more poetic way of saying what we now usually express as 'in a row.'
You'll find this word in Shakespeare and older literature—it's basically the medieval English way of saying 'back to back' or 'consecutively,' and it perfectly shows how 'a' + noun combinations have slowly disappeared from English over centuries.
Complete word intelligence in one call. Free tier — 50 lookups/day.