pen·guin (pĕnggwĭn, pĕn-)
1. Any of various stout, flightless aquatic birds of the family Spheniscidae, of the Southern Hemisphere, having flipperlike wings and webbed feet adapted for swimming and diving, short scalelike feathers, and white underparts with a dark back.
2. Obsolete The great auk.
[Possibly from Welsh pen gwyn, White Head (name of an island in Newfoundland), great auk : pen, chief, head (from Middle Welsh penn; see pendragon in the Appendix of Indo-European roots) + gwynn, white; see weid- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.