: a system in the body that controls the occurrence of natural processes (such as waking, sleeping, and aging)
What made you want to look up biological clock? Please tell us where you read or heard it (including the quote, if possible).
Take our visual vocab quiz
A quick quiz about stuff worth knowing
The commonly misspelled words quiz
The Vocab Quiz Game for iPhone & iPad
"Incredibly fun and addictive. And informative!" User Review, iTunes