A super tuck is any aero position extreme enough that your butt is no longer on the seat of the bike. Most commonly it's on the top tube, but not always. This is reasonable easy to Google.

Often a super tuck involves resting some part of the body on the top of the handlebars other than the hands.

By one armed I mean an asymmetrical position in which only one hand is on the handlebars, and the other is behind your back. This kind of asymmetry is common in speed skating, especially short track speed skating, but apparently quite uncommon in cycling.