Monster Manual, page 155
Multiattack. The giant makes two greatclub attacks.
Greatclub. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 18 (3d8 + 5) bludgeoning damage.
Rock. Ranged Weapon Attack: +8 to hit, range 60/240 ft., one target. Hit: 21 (3d10 + 5) bludgeoning damage.
Variant: New Giant Options
Some adult hill giants like to hurl themselves bodily at smaller foes and crush them beneath their bulk. This ability is represented by the following action option.
Squash. Melee Weapon Attack: +8 to hit, reach 5 ft., one Medium or Smaller creature. Hit: 26 (6d6 + 5) bludgeoning damage, the giant lands prone in the target's space, and the target is grappled (escape DC 15). Until this grapple ends, the target is prone. The grapple ends early if the giant stands up.
Source: SKT, page 246
Hill