stool

fall between two stools (mainly British, mainly British)

if something falls between two stools, it fails because it is neither one type of thing nor another and if someone falls between two stools, they fail because they try to combine two different types of thing that cannot be combined. For me, it fell between two stools, being neither romantic fiction nor serious literature. If you try to organize an event that will appeal to both young and old, you can end up caught between two stools.

See also: between, fall, two

a stool pigeon

a person, especially a criminal, who secretly gives information to the police in order to help them catch other criminals. Once they discovered he was a stool pigeon, it was only a matter of time before they had him killed.

See also: pigeon