rule of thumb
Preserved but no longer current.
Meaning · English
A rough, guesswork measure; practice or experience, as distinguished from theory. In some places the heat required in brewing is determined by dipping the thumb into the vat.
Era: ca. 1898 (Victorian)
Sources & notes
Reproduced from Brewer’s Dictionary of Phrase and Fable (1898 edition, public domain; archive.org, retrieved 2026-07-31; OCR text, minor errors possible). Reflects the scholarship and attitudes of its era.
Common questions
What does “rule of thumb” mean?
A rough, guesswork measure; practice or experience, as distinguished from theory. In some places the heat required in brewing is determined by dipping the thumb into the vat.
Is “rule of thumb” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.