taru-adjective, adverb taking the 'to' particle
with shining, piercing eyes
A yojijukugo describing a sharp, penetrating gaze that seems to gleam. Often used in literary or dramatic descriptions of intense, perceptive looks.
彼は眼光炯々として相手を睨みつけた。
He glared at his opponent with piercing, shining eyes.
その老探偵は眼光炯々たる目つきで証拠を見抜いた。
The old detective saw through the evidence with his sharp, gleaming eyes.
A related yojijukugo meaning to read between the lines or perceive hidden meanings, literally 'eyesight penetrates the back of the paper'. While 眼光炯々 describes the quality of the gaze itself, 眼光紙背に徹す focuses on the depth of understanding.
A yojijukugo composed of 眼光 (eye light, gleam of the eye) and 炯々 (shining, bright). The exact historical derivation is uncertain, but the phrase is conventionally used to describe a piercing, luminous gaze.