defense mechanism

I think it’s sort of her defense mechanism — if I get there first, no one can get to it before me.

“Growing up undocumented you grow skeptical, with a nonstop defense mechanism. Even though I’ve seen co-workers get permits, I haven’t accepted it,” A. said.

Scientists believe that algae use bioluminescence as a defense mechanism — to scare off hungry sea creatures or call attention to their location, which draws the predators’ predators.

But it's not long into the second season where all of Alice's defense mechanisms come crumbling down.

My greatest fears began to unfold as I crept back into the only defense mechanism I’ve ever known.