I turned around and he was in the middle of the floor hands and feet on the floor butt in the air. (askmoxie.org)
Sometimes he'll cry, sometimes he'll manage to scoot away with his bare butt in the air. (babygaga.com)
An indoor cat who wants to get outside can also indicate a heat cycle, while the estrus posture of butt in the air with tail tilted to one side may be the most telling sign. (thesprucepets.com)