14.23 Attacker‘s units in one hex may attack units in two or more adjacent hexes, treating it as one attack. All attacking units must be adjacent to (or on top of) all the defending units they are attacking.
I have always assumed that the portion I have underlined refers to hexes adjacent to the attacker. However, I realize that it is (surprise!) a bit ambiguous, as it could be referring to the defenders needing to be adjacent to each other.
I am wondering if there is a consensus on this one way or the other, or if there are differing interpretations.