Bo·hai Sea or Bo·hai Gulf (b??h??) An inlet of the Yellow Sea on the northeast coast of China formed by the Shandong and Liaodong Peninsulas. Its western arm is Bohai Bay.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.