The level of the ocean's surface, especially the level halfway between mean high and low tide, used as a standard in reckoning land elevation or sea depths. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "sea level" in a sentence
"The city of Kabul sits six thousand feet above sea level and is rimmed by snow-tipped mountains."
"During a subsequent glaciation, when the sea level again fell, some individuals of Micropanthera balica might have roamed back across the muddy isthmus to Java."
"The most unlikely option was the easternmost route, the Khawak Pass, at twelve thousand feet above sea level the highest and most difficult trail north through the Hindu Kush into Bactria."