Broadly, a meme is just an element of a system (usually: culture or behavior) that is transmitted through imitation.
The term comes from the Ancient Greek mīmēma, “imitated thing”, shortened to resemble the word “gene”, as a way to mirror the two concepts.
“peer-to-peer (horizontal) transmission” (or “virus of the mind”) as a proven, empirical fact. when the brain picks up something that it deems fascinating, it wants to spread it.
“social mirroring”
memes as not just culture themselves but vectors for culture and types of thought