Definitions for jet lag
Random House Webster's College Dictionary
a temporary disruption of the body's normal biological rhythms after high-speed air travel through several time zones.
Origin of jet lag:
fatigue and sleep disturbance resulting from disruption of the body's normal circadian rhythm as a result of jet travel
Kernerman English Learner's Dictionary
a tired feeling from traveling to another time zone
to suffer from jet lag
A physical condition caused by crossing time zones during flight; often the result of disruption to the circadian rhythms of the body.