The dwarf gains:
Defensive Training: Dwarves gain a +4 dodge bonus to AC against monsters of the giant subtype.
If a dwarf was wild shaped into a Huge creature such as a dinosaur would he still benefit from this trait vs a giant?
Yes.
Going by the description, the benefit is a consequence of training rather than form, so you should be good to go, same as if you were enlarged somehow to be a really big dwarf. Expect table variation, though.
You may be interested to know that there are even medium sized giants. Flood trolls and Sewer trolls.