Black's Law Dictionary (2nd edition)dictionaries

Lucid Intervals

In medical ju-risprudence. Intervals occurring in the men-tal life of an insane person during which he is completely restored to the use of his reason, or so far restored that be has suffl-dent intelligence, judgment, and will to enter Into contractual relations, or perform other legal acts, without disqualification by reason of his disease. See Insanity

Source: Black’s Law Dictionary 2nd Ed (1910)