The Collaborative International Dictionary
Cotidal
Cotidal \Co*tid"al\ (k?-t?d"al), a. Marking an equality in the tides; having high tide at the same time.
Cotidal lines (Phys. Geog.), lines on a map passing through places that have high tide at the same time. [1913 Webster] ||
Wiktionary
cotidal
a. Describing the locations (and of related lines on a chart) linking places where tides occur at the same time of day