Help with unknown plant?

I was in a short forestry training session on the three poisonous plants. I know my poisonous plants really well, Poison Oak, Poison Ivy, and Poison Sumac. However, the instructor said that Poison Oak has "5 leaves" and described them (not in these words) palmate arranged... meaning the leaves radiate from a single point. Yes, granted this instructor was new and young, but I KNOW that Poison Oak does not have 5 leaves, and does not look anything like what was drawn on the board. Just because I am curious to see what this was mistaken for, what was the plant they probably drew? I live in the Eastern United States if it helps, and here is some more detail on the visual description of the plant: 5 leaves, radiating palmate from a point, the three leaves going forward on the set being bigger than the two pointing the opposite direction.