This is just a guess, but I suppose maybe it means your pet can hardly be surprised? Like, maybe by pets coming out of the shadows or... something...
If not, then maybe it can't flinch? Since it rarely gets surprised.
But I don't know the REAL meaning of the trait, but... some reflexions to give you to think over...
Heheh.
You should wait for Kodai or Trait-specialist Admin/Mod. :3