Definition of "labium" [‖La•bi•um]

• Anatomy Any of four folds of tissue of the female external genitalia. (noun)
• Zoology A liplike structure, such as that forming the floor of the mouth of certain invertebrates, especially insects. (noun)
• Zoology The inner margin of the opening of a gastropod shell. (noun)
• Botany One of the liplike divisions of a labiate corolla. (noun)

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.

• "At the tip of the labium are the labellæ, two little lobes which serve to guide the piercing organs."
• "The labium, which is the largest and most conspicuous, is apparently cylindrical but is grooved above throughout its length."
• "The labium was the equivalent of the hyoid, the labial palps and maxillipedes the equivalent of the "hyoid" elements which form the branchial arches."