Asleep
Asleep adjective - In a state of sleep.
Usage example: fell asleep at the wheel
Fast asleep and asleep are semantically related. in sleeping topic. In some cases you can use "Fast asleep" instead the word "Asleep" as an adjective or an adverb.
Fast asleep
Fast asleep adjective - Sleeping deeply.
Usage example: lying fast asleep on the sofa
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Synonyms for Fast asleep
Asleep and fast asleep are semantically related. You can use "Asleep" instead an adjective phrase "Fast asleep".
Mutual synonyms
Cite this Source
Fast asleep and Asleep. (2016). Retrieved 2026, August 02, from https://thesaurus.plus/related/asleep/fast_asleep
Asleep & Fast asleep. N.p., 2016. Web. 02 Aug. 2026. <https://thesaurus.plus/related/asleep/fast_asleep>.
Fast asleep or Asleep. 2016. Accessed August 02, 2026. https://thesaurus.plus/related/asleep/fast_asleep.
Google Ngram Viewer shows how "asleep" and "fast asleep" have occurred on timeline