Generally, ‘posh’ denotes the English upper classes. However it can be used to describe anything flashy or needlessly classy or expensive. It is similar to the American word ‘fancy’, however it has a much more entrenched class basis.

In this way “posh” can be used in the following two ways:

• I’m going to a posh restaurant tonight.
• Have you met Bob’s girlfriend? She’s pretty posh.