like a chicken with its head cut off

In a frenzied manner, distractedly, crazily. For example, She ran around the station looking for her lost bag like a chicken with its head cut off. This graphic simile alludes to the fact that the body of a chicken whose head has been cut off sometimes totters about crazily before succumbing.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.