from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A nematode worm (Syngamus trachea) that infects the tracheas of certain birds and causes gapes.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A parasitic nematode worm, Syngamus trachea, that infects the tracheas of some birds and causes the disease gapes
from the GNU version of the Collaborative International Dictionary of English
- n. The parasitic worm that causes the gapes in birds. See Illustration in Appendix.
from The Century Dictionary and Cyclopedia
- n. A nematoid worm, Syngamus trachealis, the cause of gapes in fowls.
Sorry, no etymologies found.
 Gapeworms "lodge in the hen's throat" ... nuts! The larvae of the gapeworm live and mature in the lungs, trachea and bronchi, causing a severe pneumonia in young birds.