Wiktionary
vb. 1 (context transitive of intangibles English) To let go, allow, release, pass over without action. 2 (context transitive of persons English) To tolerate a violation of a norm from. 3 (context idiomatic English) To allow the condition of something to deteriorate due to negligence or apathy.
Usage examples of "let slide".
At home, at work on the business he let slide while he was with her?
He knew all the regulars on the street now, and was now learning to spot what was different, to eyeball it as a seasoned cop could, to decide what to check out and what to let slide.
I chewed at the inside of my lip as I stared, knowing that you give away how much you know by the questions you ask, but the terrace question was one I couldn't let slide.
Nynaeve being Nynaeve, she probably would have preferred to let slide what she did not know and could not do.
She would catch up on all the little self-indulgent activities that she had let slide, neglected, while she investigated the datablock.
Then what you gonna do, kick yourself in the ass for all the opportunities you let slide?
To avoid seeing the daughter she let slide from her fingers so long ago.