The first centimetre of the anus, usually including the sphincter.
"Man, when I stick the tip of my finger into my frostick I sometimes get a bit of grime under my fingernail!"
"Dude, do me a favour and see how far you can get your tongue into my frostick, will ya?"
"If the human body was a street map, the frostick would be a side street off Bifkin Lane"
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