"dart" generally describes a fastball—often hovering in the 96–100+ MPH range—thrown with such pinpoint precision that it looks like a dart being thrown at a bullseye. Popularized by Pitching Ninja but common well before the twitter era.
Haven't paid above $25 this year off Stubhub for a Cubs game that wasn't a bobblehead, sox, or opening day. Got a bleacher last homestead for $15. Never buy from the Cubs box office.
He's a clear upgrade over what's hitting the waiver wire, former first round pick, all star first half last season, getting away from that Mets defense/ Org.