The scissors kick is similar to the common “six inches” but much more dynamic.
Start out lying on your back with your legs out straight. Place your hands under your lower back with palms facing down (to support your back.)

Now you’ll raise your legs and shoulders.
Raise your legs about 3-6 inches off the floor. Then raise your shoulders off the floor and push your elbows into the floor for support. Be sure to keep your abs tight.

The exercise involves taking one leg over the other and “scissoring” your legs. The left leg goes up and to the right while the right leg goes down and to the left. Then the left leg comes back and goes down while the right leg comes back and up. Then scissor your right leg up and to the left, and your left leg down and to the right.

Keep repeating.

This works your transverse abdominals and really works the thighs, even in ways cycling does not (to keep your legs balanced for a better pedal stroke.)
A great stomach wokout which i was told once which is similar was to lie on your back as shown above with your legs straight and try writing your name and address and whatever else with your legs keeping them straight. The constant bending, raising and lowering provides a great burn on your obliques and abs.
Too funny! We used to write out the alphabet in the air when I was in the army. Just like Markstraining was saying above. You always look forward to the ‘w’ the ‘m’ and the ‘z’ lol