Break signal in Terminal

try ctrl-\ for crtl-break command
I was just looking for this answer as well. It works in iTerm at least.

e.g. if you want to send a sigquit to a running java process to get a stack dump

Break is a serial comm line feature that causes the TxD line to go "Low" for a specific period of time. Terminal does not do serial comm lines, so what are you sending a break signal to?

If you do need to talk with a serial port, you can run the 'screen' command (see "man screen"). There is a 'break' command as part of the 'screen' environment.

Perhaps you're looking for the Unix kill command. It will send a signal to any process on the system. You'll need the process id which can be found using the ps command or Activity Monitor. Use 'man kill' to read the manual page.

Control-c