Voltage source or Constant voltage supply or the like are the most specific. However, the vast majority of power supplies are constant-voltage, so that is what is usually assumed if you just say power supply. There are other types of power supplies, with constant current being the next most common. For example, to power LEDs you want to control current, not voltage.
If you see just power supply without a specific context or more details, you can usually assume that means a constant-voltage supply. Since something like a constant current supply is less common, that is usually explicitly stated.