Out to lunch Slang Not in touch with the real world; crazy. (idiom)
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 "lunch" in a sentence
"One who loses his lunch is a chudder and an appointment that greedily downs fast food before the session is a taco valve."
"I have been a member for about 10 years now (wow, has it really been that long?), and this lunch is always one of the more enjoyable lunches."
"Watching a bear climb into our truck and steal our lunch is my best one."