Medical Definition of orexin
: either of two neuropeptides ( orexin A and orexin B ) that are produced in the hypothalamus and play a role in regulating wakefulness and food intake Scientists have known for almost a decade that narcolepsy is caused by a dearth of a brain communication chemical called orexin.— Laura Sanders, Science News The new sleep aids block the activity of brain peptides called orexins.— Christine Soares, Scientific American
— called also hypocretin
Love words? Need even more definitions?Merriam-Webster unabridged
Words at Play
Ask the Editors
Brand Name Vocabulary Quiz
You’re gonna need some moxie to ace this quiz
Commonly Confused Words Quiz
Take a (break/brake) and (pore/pour) over this (c...
How Strong Is Your Vocabulary?
Test your vocabulary with our 10-question quiz!
Spelling Bee Quiz
Can you outdo past winners of the National Spelli...