The giant scorpion is a monster added in SLASH'EM. As the name implies, it is a far stronger version of a scorpion. A giant scorpion is not considered a grown up scorpion however; a scorpion will not become a giant scorpion through level gain and the egg of a giant scorpion will immediately produce a giant scorpion, not a scorpion.
These monsters are a major threat: they possess good speed, many hit points, and can inflict a large and steady stream of damage. One should be particularly careful if one lacks poison resistance, but even with it they remain formidable foes. Elbereth, powerful pets and/or attack wands, and possibly escape items are all advised. Be very careful not to confuse them with the scorpions with whom they share a glyph: they have three times as much health and hit approximately five times as hard.