A fork of Rural Dictionary
m/w can be often spotted in a bio, typically on discord or twitter with a name or @ usually followed after. it stands for "matching with" which indicates the context between a pfp to show who has the other half of the picture.
Person 1: Hey, what's your pfp?
Person 2: Oh, I'm just m/w my friend John. He wanted to match profile pictures so I agreed.
Short for Merriam-Webster, it is the online version of one of the best selling companies for dictionaries and other language guides.
I couldn't find my normal Merriam-Webster dictionary laying around, so I checked out m-w online!