Lewd; obscene; pornographic; blue, dirty: He uttered a few well-chosen X-rated words
[fr the now-superseded early 1950s system of rating movies according to the amount of sex, verbal obscenity, violence, etc, they contain, X being the most censorious rating]
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with X-rated
Sexually explicit, vulgar, or obscene, as in This film should be X-rated; it's not suitable for children. This expression alludes to a rating system established for motion pictures, in which films rated X may not be viewed by persons under the age of 17.
[ c. 1970