an extra second intercalated into the world's timekeeping system about once a year, made necessary by the gradual slowing down of the earth's rotation.
Why Do We Have Leap Year?In order to keep the calendar cycle synchronized with the seasons, one extra day is (usually) added every four years as February 29th.
Malpractice, Malarkey, And Other Words From The Second Democratic DebateHere's our roundup of top terms that created buzz on Dictionary.com during the second Democratic debate. For the first five words, we can thank the 10 candidates from the first night of the debate on July 30, and for the second five, the remaining 10 debating on July 31.
Origin of leap second
First recorded in 1970–75
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for leap second
a second added to or removed from a scale for reckoning time on one particular occasion, to synchronize it with another scale
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
Science definitions for leap second
[ lēp ]
A second of time, as measured by an atomic clock, added to or omitted from official timekeeping systems annually to compensate for changes in the rotation of the Earth. See more at coordinated universal time.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Culture definitions for leap second
A second inserted into the year to make up for the fact that the Earth's rotation is slowing down.
Scientists know when to insert a leap second by comparing the Earth's rotation to an atomic clock.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.