The Million Dollar Question

[Confused Ape]

No the definition would still apply, each of those gods or goddesses were supreme in one attribute or domain.

Okay, let's use that definition.

The Egyptian Ra

Ra /rɑː/[1] or Re /reɪ/ (Egyptian: ?ꜥ, rˤ) is the ancient Egyptian solar deity. By the Fifth Dynasty (2494 to 2345 BC) he had become a major god in ancient Egyptian religion, identified primarily with the midday sun.

All forms of life were believed to have been created by Ra, who called each of them into existence by speaking their secret names. Alternatively humans were created from Ra's tears and sweat, hence the Egyptians call themselves the "Cattle of Ra."

So, he was a sun god and a creator but he wasn't supreme in the creation domain because -

Amun was a member of the Ogdoad, representing creation energies with Amaunet, a very early patron of Thebes. He was believed to create via breath, and thus was identified with the wind rather than the sun.

Eventually -

As the cults of Amun and Ra became increasingly popular in Upper and Lower Egypt respectively they were combined to create Amun-Ra, a solar creator god. It is hard to distinguish exactly when this combination happened, but references to Amun-Ra appeared in pyramid texts as early as the fifth dynasty. The most common belief is that Amun-Ra was invented as a new state deity by the Theban rulers of the New Kingdom to unite worshipers of Amun with the older cult of Ra around the 18th dynasty.[10]

If Ra had been real he would have suffered something of an identity crisis because he was merged with other gods as well. For example -

Khepri was a scarab beetle who rolled up the sun in the mornings, and was sometimes seen as the morning manifestation of Ra. Similarly, the ram-headed god Khnum was also seen as the evening manifestation of Ra. The idea of different deities (or different aspects of Ra) ruling over different times of the day was fairly common, but variable. With Khepri and Khnum taking precedence over sunrise and sunset, Ra often was the representation of midday when the sun reached its peak at noon. Sometimes different aspects of Horus were used instead of Ra's aspects.

We mustn't forget Aten.

Aten (also Aton, Egyptian jtn) is the disk of the sun in ancient Egyptian mythology, and originally an aspect of Ra.

The solar Aten was extensively worshipped as a god in the reign of Amenhotep III, when it was depicted as a falcon-headed man much like Ra. In the reign of Amenhotep III's successor, Amenhotep IV, the Aten became the central god of Egyptian state religion, and Amenhotep IV changed his name to Akhenaten to reflect his close link with the new supreme deity.[1]

The full title of Akhenaten's god was "Ra-Horakhty who rejoices in the horizon, in his Name as the Light which is in the sun disc." (This is the title of the god as it appears on the numerous stelae which were placed to mark the boundaries of Akhenaten's new capital at Akhetaten, modern Amarna.) This lengthy name was often shortened to Ra-Horus-Aten or just Aten in many texts, but the god of Akhenaten raised to supremacy is considered a synthesis of very ancient gods viewed in a new and different way. The god is also considered to be both masculine and feminine simultaneously. All creation was thought to emanate from the god and to exist within the god. In particular, the god was not depicted in anthropomorphic (human) form, but as rays of light extending from the sun's disk.

The Egyptians weren't ready for this. After Akhenaten's reign Ra went back to being the version of Ra they preferred.

So, let's try this as a definition - a deity is a supernatural being whose attributes and domain depend on whatever the theology of the time is.