sack⁴ or sacque /sak/ (historical)

1. A woman's loose-fitting gown (also sack dress)
2. A train of silk hanging from the shoulders of such a gown
3. A woman's hip-length coat with a loose-fitting back

• on bended knee
• on board
• on-board
• onboard
• ONC
• on call
• on camera
• once
• once-accented
• once again
• once and again
• once and for all
• once bitten, twice shy
• once-errand
• once for all
• once-for-all
• once in a blue moon
• once in a way
• once in a while
• once more
• once or twice
• once-over
• once-overs
• oncer
• oncers