It means you should have read the manual when you got the phone
So if i were you, id go into my 'settings and tools' from the menu. Then go into 'phone info' then scroll down to 'icon glossary' then look for your mystery symbol there :)
The toner cartridge is almost empty.
whats a mobile phone?
I'd drop in to a place that sells phones and ask them if I no longer had the manual
my guess would be email, you can google your phone model and company and you should be able to find out.. or if you have the owners manual you can find there also
Maybe your inbox is full or something...