saえるeru
1.

To experience a heightened clarity in perception, where sights, sounds, and colors appear distinctly sharper and more vivid, often like on a cold, clear night.

2.

To exhibit heightened mental acuity or alertness, where one's thoughts and awareness are particularly sharp and focused, often described as having a clear mind.

3.

To show exceptional skill or proficiency, especially in a manner that stands out due to its brilliance or finesse, reflecting a high level of expertise.

4.

To be overcome with a sense of freshness and liveliness, often used in the context of one's expression or presence being vibrant and full of energy.

Example:

満月が空にさえている。