1. Of, relating to, or occurring in the night: nocturnal stillness.
2. Botany Opening at night. Used of flowers.
3. Zoology Most active at night: nocturnal lizards.
[Middle English, from Old French, from Late Latin nocturnālis, from Latin nocturnus, from nox, noct-, night; see nekw-t- in the Appendix of Indo-European roots.]
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