Aside from speculations of the title coming from Tarantino's mispronunciation of the French film name, what meaning does Reservoir Dogs have in context of the actual story line?
According to Urban Dictionary:
A rat. Slang term for one who snitches to the police, or is an undercover police officer themselves. Origin comes from the great size of rats living in and around reservoirs.
Near the end of the movie, the survivors come to a dramatic conclusion, one of them is a snitch or a cop. The title is actually a very good title, a reservoir is something that holds stuff inside (no get out) and dogs (criminals) see the diamond as a bone.
This is just my point of view, Tarantino himself bragged how cool it is for people to come up with their own significations, I don't think there is one set in concrete.
I don't want to sound rude or anything, but OP clearly stated that he wanted another answer than the one IMDb states with Quentin's French words being messed up.
What does the title mean?
Tarantino doesn't typically answer this question directly, saying that he likes it when people come up with their own definitions for the phrase. He has called it "more of a mood title than anything else." One popular and oft-told story about the origin of the title is that former video store employee Tarantino used to mangle the title of the French film Au revoir les enfants, and his mispronounciation gave birth to the phrase "Reservoir dogs." Lawrence Tierney (who plays Joe Cabot) reportedly told a German reporter that Reservoir dogs was "a very famous expression in America for dogs who hang around a reservoir.