The 'Ensnare' trait is available on weapons only.

How it works:
Non-bodyshot attacks have a chance to root the target for one turn. The chance is {x}% for melee and {y}%  for ranged classes.

The trait is affected by the 'Lucky' trait, and is available on all survivor classes.

Remember that Rooted enemies are still able to attack you if your survivor is adjacent to them.