An empty space or a missing part; a gap: "self-centered in opinion, with curious lacunae of astounding ignorance” ( Frank Norris).
Anatomy A cavity, space, or depression, especially in a bone, containing cartilage or bone cells.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.