Definition of a Crowded Trade

I've read in several places that when researching stocks one of the things that you should consider is how crowded the trade is. However, I've never really seen anyone give a more specific definition of what that means.

1) Are asset managers included in what's considered a crowded trade? For instance, if a few HFs make up only 5% of a company's stock, and 90% is with the Fidelity's or vanguards of the world and the rest with insiders, is this considered a crowded trade too?

1a) If mutual funds are included here, then I guess what would not be considered a crowded trade? I.e. One that is only owned by insiders? If that's the case, doesn't this basically exclude every stock that isn't a penny stock (I could be very wrong here, but I'm assuming most companies above $500M market cap are going to have at a minimum a significant mutual fund ownership %, this could be a false assumption).

2) What % is a good cut off to look at?

Thanks in advance for the stupid question.