Crummy, cruddy, crappy, or otherwise not very good.
This made-up term, intended as a spoof of teenage slang of the day, was first used the the 1947 RKO motion picture, "The Bachelor and the Bobby-Soxer" starring Cary Grant, Myrna Loy, and Shirley Temple. In the opening scene, when a maid wakes
teenager Susan Turner, played by Temple, she protests being woken, saying "But, Bessie, I feel absolutely sklonklish." Moments later, when Bessie relates the conversation to
Susan's older sister, Judge Margaret Turner, played by Loy, the sister says, "Next
time she tells you she feels sklonklish, you tell her not to be a clunk."