A shortening and also offensive slang for someone with Aspergers, or someone who displays similar obsessive behavior as the usual symptoms of Aspergers syndrome.
One common symptom of Aspergers is that the person becomes so obsessed with a particular topic that, in conversation, they will endlessly ramble on about it.
Sperg is something you would call a person who doesn’t necessarily have Aspergers, but talk so much about one specific topic that what started as conversation has gone over to a monologue.
It can be both a noun, and a verb, such as “sperging” or to “sperg out” too much information.
The slang appeared on the Google newsgroup rec.games.miniatures.warhammer in 2009, when user “Playa” made a comment about how narcissistic and awful “spergs” are, for behaving like everyone else are “lesser” beings.
In 2014 “Anonymous” commented on a “World of Darkness” forum about how he could “sperg on” about werewolves.
The term is usually used online, often in online games and in gaming culture.
If a person starts talking or writing in too much detail about something in the videogame, other gamers will comment that they are “spergs” or “sperging out”.
Often, people who actually have Aspergers will react negatively to the term, while others don’t mind it.