if a thought, etc. is at the back of your mind, you are aware of it but it is not what you are mainly thinking about
Oxford100% of films
if a thought, etc. is at the back of your mind, you are aware of it but it is not what you are mainly thinking about
I have to admit, in the back of my mind I was praying, he wouldn't get fresh and all of the while I was wondering why and a little bit girl should attract him, then all of a sudden he said, I couldn't go wrong with the way of all flesh.
Definitions from the Oxford Advanced Learner's Dictionary, 9th edition