/ Dictionary / Index R Regulation U: Meaning and Definition of Find definitions for: Regulation U Pronunciation: [key] (in the U.S.) a federal law governing the amount of credit that may be advanced by a bank for the purchase of listed securities. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Regulation T regulator Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language