Symbol similar to thermistor
That image came from Rapid Online and while it's still available in the location you've linked to it's been removed from their General Purpose Power Relays 7A 4PDT page where it used to be. So it looks like the symbol they've used for a regular 4PDT power relay. 

You can view a version of the page as at March 2, 2013 on The Internet Archive that includes the image.