hill·y (h?l??)adj. hill·i·er, hill·i·est 1. Having many hills.2. Similar to a hill; steep.hill?i·ness n.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.hill?y (?h?l i) adj. hill?i?er, hill?i?est. 1. full of hills; having many hills. 2. resembling a hill; elevated; steep. [1350?1400] hill?i?ness, n. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.