[sem-ee-dahy-ur-nl, sem-ahy-]


pertaining to, consisting of, or accomplished in half a day.
occurring every 12 hours or twice each day.

Origin of semidiurnal

First recorded in 1585–95; semi- + diurnal Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for semidiurnal

Historical Examples of semidiurnal

  • The semidiurnal tidal forces vanish at the Pole and are very small over the entire Arctic Ocean.

    The North Pole

    Robert E. Peary

British Dictionary definitions for semidiurnal



of or continuing during half a day
occurring every 12 hours
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