A story that is absurd or ridiculous. Please don't get involved if he tells you another cockamamie story of how you'll get rich quick working on his latest invention—you know they never pan out. When I asked Tommy why he didn't have his book report to hand in, he gave me some cockamamie story about it flying into the fireplace last night.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.