Dictionary.com
definitions

comparative advertising

noun
  1. advertising in which a competing product is identified and compared unfavorably with the advertiser's product.

Origin of comparative advertising

First recorded in 1970–75
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for comparative advertising

comparative advertising

noun
  1. a form of advertising in which a product is compared favourably with similar products on the market
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