From Longman Dictionary of Contemporary Englishlight sleep/dozelight sleep/dozeSLEEPa sleep from which you wake up easily I fell into a light sleep. → light
Examples from the Corpus
light sleep/doze• About two hours every night is spent in light sleep.• I'd been in a light sleep.• Then a sudden wave of exhaustion swept over her, and she slid into a light doze.• Corbett fell into a light sleep and was awakened by Ranulf with the news that the ferrymaster had returned.• Stages 1 and 2 are stages of light sleep, just drifting off and being asleep but easily aroused. 