The ability for a person to sit and put either right OR left leg up on the other knee.
Because he was ambilegstrous, Eddie sat for 8 hours in a meeting without having to move - he has the ability to cross either of his legs, unlike most of us who can only cross one favored leg.
The ability to use both legs with equal dexterity. Is to legs what ambidextrous is to hands.
"Is he gonna take this free kick with his left or right?" "Doesn't matter, he's ambilegstrous."