to be open their jacks
Preserved but no longer current.
Meaning · English
To have the advantage over one. The reference is to the jack, or jerkin, a coat of mail quilted with stout leather.
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 “to be open their jacks” mean?
To have the advantage over one. The reference is to the jack, or jerkin, a coat of mail quilted with stout leather.
Is “to be open their jacks” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.