Acute or penetrating in intellect or perception. Of sight, hearing, the eyes or ears: Acute, keen. Often in figurative expressions.

Keenly perceptive; capable of ready perception, alert. Of the senses. Now somewhat archaic.

Of a feeling, sense, sensation, etc.: acute, keen.

Of the senses or nervous system: keen, sharp, quick in catching or responding to impressions. Hence, of the emotions: sensitive to impressions…

Lively, animated; (of the senses or intellect) keen, attentive, aware.

Of the eyes or eyesight: Sharp, penetrating. Hence, of hearing, smell, or other sense: Acute, highly sensitive. Also of persons or animals: Sharp of…