a. [CO- 2.] Of or pertaining to the coincidence in time of tidal phenomena, esp. that of high water. Cotidal line, a line on a map connecting all those places at which high water occurs at the same hour.
1833. Whewell, in Phil. Trans., 151. The cotidal lines so produced will be nearly perpendicular to the length of the sea.
1858. Merc. Marine Mag., V. 164. ‘Co-tidal line’ … a line passing through all those points which have high water at the same hour of the day.
