What is it called when ankles buckle outward? what can i do to prevent this? happens to both ankles and nearly causes fall.

Weak ankles: Ankle weakness is more common in previously injured joints. If an ankle is sprained and doesn't get properly rehabbed afterward, it will remain weaker than it was before injury. I would advise consulting a physical therapist for a rehab program if you have a history of recurrent ankle sprains. Also see your doc, since ankle weakness can occur with some neurologic conditions.

Ankle instability: It sounds that you have loose ankles. The vast majority of loose ankles will respond to a physical therapy program which focuses on increasing the muscle strength, balance re-training, and something called proprioception re-training. Proprioception is body awareness. It allows you to take corrective action to avoid a bad ankle sprain.