sooty ternn. A widespread pelagic tern (Onychoprion fuscatus) primarily of tropical waters, having black plumage above and white below. Also called wideawake.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.soot?y tern? n. a black-and-white tern, Sterna fuscata, of small tropical islands. [1775?85] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.