Does Meekstone prevent untapping of a creature with exactly 3 power?

Meekstone reads: 'Creatures with power 3 or greater don't untap during their controllers' untap steps.' The phrase 'power 3 or greater' includes exactly 3, so a creature with a power of precisely 3 is affected and will not untap during its controller's untap step.

This is a static ability that creates a continuous effect under CR rule 604.1. It applies during the untap step (CR 502.1), preventing the normal untapping that would otherwise happen automatically for all permanents the active player controls (CR 502.2).

The creature's power is checked as the untap step begins. If something were to reduce the creature's power to 2 or less before untapping is processed, Meekstone's restriction would no longer apply to it at that moment.

Example: Your opponent controls a Grizzly Bears (2/2) and a Hill Giant (3/3). During their untap step, Grizzly Bears untaps normally, but Hill Giant — with exactly 3 power — remains tapped because of Meekstone.