A type of sleep cycle, related to diurnal and nocturnal. It refers to a creature that doesn't sleep JUST at night (like humans) or JUST during the day (like owls and bats), but instead naps at various times, both day AND night, throughout a 24 hour period.
Cats take cat naps because they are cathemeral.

College students often become cathemeral after excessive partying and late-night studying.
by KatrinaLC August 6, 2011
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