Fast asleep and Sound asleep

Fast asleep

Fast asleep adjective - Sleeping deeply.
Usage example: lying fast asleep on the sofa
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Synonyms for Fast asleep

Sound asleep is a synonym for fast asleep. In some cases you can use "Sound asleep" instead the phrase "Fast asleep" as an adjective or a noun or an adverb.

Sound asleep

Sound asleep adjective - Sleeping deeply.
Usage example: he's sound asleep
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Synonyms for Sound asleep

Fast asleep is a synonym for sound asleep. You can use "Fast asleep" instead the phrase "Sound asleep" as an adjective or a noun or an adverb.
Cite this Source
Sound asleep and Fast asleep. (2016). Retrieved 2026, August 02, from https://thesaurus.plus/related/fast_asleep/sound_asleep
Fast asleep & Sound asleep. N.p., 2016. Web. 02 Aug. 2026. <https://thesaurus.plus/related/fast_asleep/sound_asleep>.
Sound asleep or Fast asleep. 2016. Accessed August 02, 2026. https://thesaurus.plus/related/fast_asleep/sound_asleep.
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