On a doughnut or donut, the jam anus is the insertion point of Jam into a filled doughnut.
This is conducted using a baster or piping
bag, thus a puncture mark is left on the doughnut when the implement is retracted.
The term was used by
Sarah Millican in the Off Menu Podcast with Ed Gamble and James Acaster.
Episode 87:
Sarah Millican (Christmas Special) whilst discussing Greggs doughnuts (29:11)