1. A unit of weight formerly used in Spanish-speaking countries, equal to about 11.3 kilograms (25 pounds).
2. A unit of weight formerly used in Portuguese-speaking countries, equal to about 14.4 kilograms (32 pounds).
3. A liquid measure formerly used in Spanish-speaking countries, having varying value but equal to about 16.2 liters (17 quarts) when used to measure wine.
[Spanish and Portuguese, both from Arabic ar-rub', the quarter (of a quintal) : al-, the + rub', quarter; see rbʿ in the Appendix of Semitic roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.