The term stone giant refers to many different, yet possibly interconnected, titan creations. All three are, of course, giants made of stone.
Some stone giants, like Archaedas, are constructs and ancient servants of the titans, and guard their vaults. Although they are significantly smaller and weaker than their god-like creators, stone giants like Archaedas are still powerful giants by human standards. Aman (if he is an actual titan) shows that this type of stone giant is supposedly in the titans' direct image.
Stone giants (also called wood giants) are found primarily in Northrend. They look like mountain giants with trees sticking out of their backs, and roots wrapped around their heads. These stone giants look more like a type of colossus. Some of the stone giants are rune-inscribed, the runes control the giants.
Stone giant (model)
Some of Northrend's stone giants are more detailed appearing more human-like with carved beards, and armor. One of their hands seems to have been replaced with a spiked boulder.
Known stone giants
Notable stone giants
Other stone giants