Physics Having an extremely low probability of occurrence. Used of quantum phenomena: a forbidden transition. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "forbidden" in a sentence
"Crazed wizards worshiping ancient things that existed millennia ago; hideous secrets scrawled in forbidden tomes of flesh; contacting evil servitors who will do the sorcerer's bidding ..."
"Still in our fine new world where everything not forbidden is compulsory, rules is rules and must be obeyed. here's my story."
"American individualism is, in short, forbidden fruit, dangerously tempting."