A syphonic aspirator, also known as a "Syvac" or "air extractor," is a small device (like a cartridge or "bomb") that fits into the tailpipe of specific older toilet syphons (like Thomas Dudley Turbo '88' or Cascade) to help create a stronger, more reliable vacuum for a powerful flush in siphonic toilets, ensuring all the water empties and the bowl cleans effectively. It essentially assists the siphon action by managing air, preventing blockage and ensuring a full, clean flush.