资料来源 : Webster's Revised Unabridged Dictionary (1913)

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.