"In ancient Rome, the plebeians or plebs were the general body of free Roman citizens who were not patricians, as determined by the census, or in other words 'commoners'." - Wikipedia
"Could nowadays be used similarly disrespectful to describe someone who doesn't 'get' good art, food, music or anything culturally relevant to you, as well as uneducated rude people in general." - Urban Dictionary
"The kind of ordinary people like us who set up TBM, trying to get by in life with some form of income from a day job, making ends meet and sharing thoughts about the world with their mates over a beer.
A Bitcoin pleb is exactly the same but they talk about Bitcoin instead whether it’s in between stacking shelves, 'working from home' or tweeting about anything related to Bitcoin to keep their minds from going numb." - The Bitcoin Manual
"In Bitcoin-speak, 'pleb' is a self-proclaimed term for an ordinary person contributing to the Bitcoin network (ie. 'stacking sats', 'HODLing', running a node, educating, etc.)" - Wotterdog
"Nostr Plebs is a NIP-05 ID and Nostr services provider built by Bitcoiners for Bitcoiners. Nostr Plebs instantly groups your profile among other users, allowing new Nostr users to easily find you and make you identifiable." - lightning network+

I'm sure this only scratches the surface.