If you try to make a telephone call and get a busy signal, it means that you cannot make the call because the line is already being used bysomeone else.
[US]regional note: in BRIT, use engaged tone
I tried the number again, got a busy signal.
busy signal in British English
noun
US and Canadian
a repeated single note heard on a telephone when the number called is already in use
Also called (especially in Britain): engaged tone
Examples of 'busy signal' in a sentence
busy signal
The phone hadn't rung for a while, and I'd just gotten another busy signal from Maria's number when I heardthe hum of the elevator.
Goldsborough, Robert MURDER IN E MINOR
I left Brenda hungrily buttering a roll, found a public telephone in the lobby, dialled the collect call, heard the busy signal.
Kallen, Lucille C B GREENFIELD - A LITTLE MADNESS
At any rate he returned home, called half an hour later and got a busy signal again.
Delman, David DEATH OF A NYMPH
In other languages
busy signal
British English: busy signal /ˈbɪzɪ ˈsɪɡnəl/ NOUN
A busy signal is a repeated single note heard on a telephone when the number called is already in use.