fast asleep
Proposed by a contributor, not yet supported by evidence.
Meaning · English
Sleeping soundly and deeply
Literally: quickly sleeping
Where it’s used:
Used
Widespread English
Examples
The baby was fast asleep in her crib
AI-drafted example auto-approved by rule (illustrative, not a corpus attestation)
Sources & notes
Listed in Wiktionary’s “English idioms” category (retrieved 2026-07-29); definition pending editorial review. Definition drafted by AI (@cf/meta/llama-3.3-70b-instruct-fp8-fast) and auto-approved by rule on 2026-07-30; pending editor spot-check.
Common questions
What does “fast asleep” mean?
Sleeping soundly and deeply Literally: quickly sleeping
Is “fast asleep” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.