The housemates have just been heard saying this to each other. You won't find much online about it as it's quite literally used when production pauses on Saturdays. It was first coined on day 6 when the first non-production day came around, to indicate to other housemates that they are talking about something that should be kept for TV.
2:25pm AEDT - More context to the "flamingo" codeword and this being an "off day". Abiola, Ed, Conor and Michael are in the kitchen. Ed says Big Brother has called "flamingo" on him over the speakers several times today. Despite Allana and Bruce coining the term, it seems Big Brother (or at least the producers on site today) have taken to using this word too.
Michael comments Big Brother is "on holiday today".
Abiola questions what Ed was talking about, and she jokes "maybe you've finally decided to open up". It appears they've been told to actively avoid conversations about...