from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A series of sharp buzzing tones heard over a telephone when the line dialed is already in use.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An audible signal to the calling party that indicates failure to complete the requested connection; an engaged tone
Sorry, no etymologies found.
He tried calling Emmett again but just got the busy signal again.