Board Thread:Questions and Answers/@comment-39481346-20190516030934/@comment-32923490-20190516200840

It means that unit has triggered it's "Survive Lethal Strike" ability.

This means that the unit survived a fatal blow, reducing it's HP to 1.

Any other hit will finish the unit off.

This means that units with this ability will need to be hit at least twice to die.

Units (and enemies) with this are Jiangshi Cat, Helmut Krabble, and Togeluga.

The chance of it activating are not always 100%