Es·a·ki (?-sä?k?), Leo Born 1925. Japanese physicist who developed a very fast and very small type of diode that is now widely used in many electronic devices, especially computers.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.