Hane-goshi (跳腰), the spring hip throw.

Nage-waza (throwing techniques), Koshi-waza (hip techniques), Gokyo 3rd set (Dai-sankyo).
Required for: 12th Mon (green belt, British Judo Association); 3rd Kyu (green belt, JudoScotland); 3rd Dan (black belt, British Judo Association); 4th Dan (black belt, British Judo Association); 5th Dan (black belt, British Judo Association).

About
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Tori enters with a bent leg pressed against uke's thigh and shin and springs both leg and hip upward together to flip uke over.

Step by step (standard right-handed form)
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1. From a right-handed grip, draw your partner up and forward so their chest comes to you and their weight floats onto their toes.
2. Step your right foot inside their right foot, pivot, and turn your back into them with your left foot supporting.
3. Bend your right leg and set it against the front of their right leg, your calf and the back of your thigh touching their shin and thigh, your foot beside their ankle: the whole bent leg lies against their leg like a fitted spring.
4. Draw them tight onto your hip with sleeve and lapel.
5. Spring: leg and hip lift together in one upward snap while your trunk tips forward and left.
6. They are flipped over your hip and springing leg and land on their back in front of you; the sleeve stays in your hand.

Key points
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1. Bend the springing leg and keep it in contact with uke's leg
2. Spring hip and leg upward as one movement
3. Draw uke tight onto your hip before the spring

Receiving it
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A bent leg fits itself against the front of your leg from ankle to thigh, their hip close, and then everything springs upward at once: you are flipped rather than rolled. The fall has snap to it. Stay compact, chin tucked, and let the held sleeve place you on your back, left arm slapping as you land.

Reference pages elsewhere
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Hane-goshi on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Hane-goshi

From Waza Book: https://wazabook.com/techniques/hane-goshi/