I.a double pipe:— in the race, a double course, in which the runner ran to the furthest point of the στάδιον, turned the post (καμπτήρ), and ran back by the other side, Pind., Soph., Eur.:—metaph., κάμψαι διαύλου θάτερον κῶλον to run the backward course, retrace one's steps, Aesch.; also, δίαυλοι κυμάτων ebb and flow, Eur.; δισσούς ἂν ἔβαν διαύλους they would twice return, id=Eur.
II.a strait, id=Eur.