1 general:: Abandon someone to danger, as in The squadron withdrew and just let us hang out to dry. This expression alludes to hanging wet laundry on a clothesline. [Slang; 1960s]
American Heritage Idioms
2 general:: Phrase(s): hang someone out to dry Fig. to defeat or punish someone. • The boss was really angry at Billie. He yelled at him and hung him out to dry.
McGrawhill's American Idioms And Phrasal Verbs