Autistic. There are many levels of tist. An alternative to the words and phrases, "retarded", "Mentally challenged", or anything else you can think of to describe someone who exhibits the kind of behavior that is frowned upon to point out in public.
One who is knowledgeable in the inner makings of a bonfire. Most importantly, the individual likes for the fire to look good throughout the entire process.
Damn max... when's that fire gonna be ready? Response: BITCH I'm a fire-tist, you can't rush perfection! Now go get me another load of wood. That's exactly why you burn up all the gasoline when your on fire duty!