To judge or criticize something. Hey, pickles and ice cream are pretty good together—don't knock it!
See also: knock
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
tv. to criticize someone or something. Don’t knock it if you haven’t tried it.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
knock/throw for a loop
Slang To surprise tremendously; astonish.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.