What does the phrase sitting up like jacky mean?

The phrase "sitting up like Jacky" is not a common or widely recognized idiom in English. It's possible it's a regional expression or a family joke.

Without more context, it's hard to say exactly what it means. Here are a few possibilities:

* It could refer to a specific person named "Jacky" who has a particular way of sitting upright. Maybe Jacky sits very straight with their back and shoulders straight, or maybe they sit with their legs crossed in a very formal manner.

* It could be a playful or ironic comment about someone's posture. Perhaps the person is sitting in a way that seems stiff or uncomfortable.

* It could be a reference to a specific joke or story. If you have any further context, such as where you heard this phrase or who was saying it, that could help determine its meaning.

To understand the meaning, it's best to try and get more information about the specific situation where you heard this phrase.