I was looking for some reference to clarify this issue on the web, and what do I see in the first couple hits on google? Bad information on the topic. It seems that a lot of sites say there is no difference between dropdown and pulldown menus. Guess what? THEY'RE WRONG!
Here's the difference:
Dropdown menu: When you click on the menu header to access the menu, the menu stays on the screen until a selection is made. Note that clicking outside the box also counts as a "selection".
Pulldown menu: You have to hold the mouse button down to access the menu. If you release the mouse button or drag off the menu, the menu goes away. In other words a PULLdown menu is a DRAGdown menu, but it is not a DROPdown menu!
A subtle difference I'm sure, but it's quite a big one in regards to UI workflow. Also note that a dropdown takes two mouse clicks. One to access the menu, and one to access the menu item. A pulldown (dragdown) only takes one click, but you must hold down the button as with a mouse drag operation.
Now is it clear? I hope so.