/ Dictionary / Index R Regulation T: Meaning and Definition of Find definitions for: Regulation T Pronunciation: [key] (in the U.S.) a federal law governing the amount of credit that may be advanced by brokers and dealers to customers for the purchase of securities on margin. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. regulation Regulation U 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