1. let sleeping dogs lie - Verb
2. let sleeping dogs lie - Phrase
let sleeping dogs lie (third-person singular simple present lets sleeping dogs lie, present participle letting sleeping dogs lie, simple past and past participle let sleeping dogs lie)
(idiomatic) To leave things as they are; especially, to avoid restarting or rekindling an old argument; to leave disagreements in the past.
Eventually, they decided it would be best to let sleeping dogs lie and not discuss the matter any further.