it's to laugh
Also, it is to laugh. It is absurd, laughable, as in You think the trial will be over in a week—it's to laugh! This expression is usually put as an exclamation, as in the example. [Second half of 1900s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.