From Longman Dictionary of Contemporary Englisha shot in the darka shot in the darkGUESSan attempt to guess something without having any facts or definite ideasMy answer to the last question was a complete shot in the dark. →shot
Examples from the Corpus
a shot in the dark• Let's see if she's at Fiona's house. It's a shot in the dark, but we've got to start looking somewhere.• My answer to the last question was a complete shot in the dark.• That was a shot in the dark, but judging from the expression on his face it struck home.