The old professor is in vigorous spirits and his mind is sharp.
Tips
usage
Mainly survives in 矍铄 ('hale and hearty'), a praising word for an elderly person who is still energetic and clear-eyed. Its old sense was 'to look around alertly', which the two-eye shape pictures.
Eye, the indexing radical, the left of a doubled pair of eyes on top. The two eyes picture a startled creature glancing sharply about, the root of the 'alert, vigorous' sense.