It's pronounced 'bye-zow', and is a commonly used derogatory term used by the Chinese to refer to hypocritical white liberal westerners who are obsessed with virtue signalling about everything from race and immigration to trans rights etc etc. It began in reference to (As they saw it) the constant meddling of westerners in Chinese affairs like Tibet, Hong Kong and the South China Sea, but has since become synonymous with all things woke. The direct translation doesn't really work, but it's an insult.
When I lived there I was often asked if I knew any in real life, comically. It's a personality type that simply does not compute.
Edit: similar vein as Malcom X's 'the white liberal is the worst enemy of the black man'.