seatmate
seat·mate
(sēt′māt′)n.
A person sitting next to another on a conveyance such as an airplane: "His seatmate was a gray-haired woman with glasses" (Anne Tyler).
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.
seatmate
(ˈsiːtmeɪt)n
US the person who is sitting in the next seat
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
seat•mate
(ˈsitˌmeɪt)n.
a person who occupies an adjoining seat.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.