You cannot judge a book by its cover Share definition Flag You cannot judge the character or quality of something/someone just by looking at them. You cannot judge a book by its cover; that girl you talked to is actually a very nice person. You cannot judge a book by its cover by Kitter the Killer Kat C: January 10, 2016 0 0 Get merch Get the You cannot judge a book by its cover mug. Buy Now — $32.95 See more merch