This is when you take on something larger than anticipated in your back passage...on pulling out it causes the expulsion of the contents of your bowels and an involuntary cry of 'woo woo' like a train.
"oh my god...you look awful...what happened to you last night"
This is the process, usually done in communal toilets, where a layer of tissue paper is put in the toilet before defacating to cushion its fall and prevent splash back. This is then covered by another layer of tissue paper thereby creating a reverse oreo cookie effect
"the toilet is blocked again"
"that's because Janet did a reverse oreo and it wouldn't flush"