An abbreviation for "bring your own," typically used of a place or event that does not serve alcohol but permits patrons to bring it with them. The restaurant is BYO, so I’ll pick up a bottle of wine on my way there.

"BYO" is an abbreviation for "bring your own." What the second "B" stands for in "BYOB" is disputed; both "bottle" and "booze" are often used. "BYOB" is typically used of a place or event that does not serve alcohol but permits patrons to bring it with them. The restaurant is BYOB, so I’ll stop and pick up a bottle of wine on my way there.