The term "toxic" refers to any ill effect on a pet... a toxicity can be as mild as some GI upset or mucosal irritation all the way to acute kidney failure and death. Just because one is toxic doesn't mean it's necessarily harmful in the sense that it will cause death. That's why it's important to look up all side effects of possible ingestion for every plant, ESPECIALLY in house holds where you have pets that can't seem to keep their little mouths off of them...

And yes, poinsettias are one of them that are toxic but not fatal if ingested, that's a good example.