the GNU version of the Collaborative International Dictionary of English
n. One of the ephemeral flies.
The Century Dictionary and Cyclopedia
n. An insect which lives but for a day or for a very short time; hence, any being whose existence is very brief.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. anything short-lived, as an insect that lives only for a day in its winged form
Word Usage
"Now several things should be noted: he doesn't say all flies have four legs; he mentions a particular animal, the "ephemeron", which is most likely a species of mayfly, or"