1. of, pertaining to, characterized by, or subject to tides: a tidal current.
  2. dependent on the state of the tide as to time of departure: a tidal steamer.

Origin of tidal

First recorded in 1800–10; tide1 + -al1
Related formstid·al·ly, adverbnon·tid·al, adjectiveun·tid·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for tidally


  1. relating to, characterized by, or affected by tidesa tidal estuary
  2. dependent on the state of the tidea tidal ferry
  3. (of a glacier) reaching the sea and discharging floes or icebergs
Derived Formstidally, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for tidally



1807, a hybrid formation from tide (n.) + Latin-derived suffix -al (1). A tidal wave (1830) is properly high water caused by movements of the tides; erroneous use for "tsunami, great ocean wave caused by an earthquake, etc." is recorded from 1878.

Online Etymology Dictionary, © 2010 Douglas Harper

tidally in Medicine


  1. Resembling the tides; alternately rising and falling.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.