any mood-altering drug, as a stimulant or tranquilizer, that does not cause physical dependence but may lead to the use of addictive drugs, as heroin.
Origin of gateway drug
First recorded in 1985–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for gateway drug
a recreational drug such as cannabis, the use of which is believed by some to encourage the user to try stronger drugs
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012