In my basic (powered) aerobatics rating, a stall turn was an inertial/vertical climb where at the minimum speed possible, full rudder was used to yaw the aircraft to a nose-down attitude. Sufficient opposite aileron was used to prevent roll and ensure exit was in the same plane/direction as entry.

A hammerhead was a tail slide. Same entry as above but no application of rudder nor aileron. Controls locked to minimise damage when you start to fly backwards and after a time, the aircraft 'self corrects' and flicks to a nose down attitude.

Both highly enjoyable in their own right but unless being flown intentionally, the latter is a consequence of the mis-flown former. I'd never attempt to hammerhead/tail slide a glider due to the resultant stress on the control surfaces unless it was specifically built for that purpose, ie the fully aerobatic ships.

Given your description, I share Kirks perspective that it's a 'stall turn' that's been lost in translation.

CJ