Log message “Disabling IRQ”: what does it mean?

This message appears in my dropdown terminal at seemingly random times when no processes is running in that terminal:

andreas@debianator:~$ 
Message from syslogd@debianator at Feb 24 18:57:58 ...
 kernel:[43089.321139] Disabling IRQ #43

I guess I can disable it from being printed with dmesg -n 1 but what does the message mean?