If you're not familiar with the term, Urban Dictionary's got your back
I'm going to do my best to keep this from turning into a rant, but no promises. To say that I'm a fan of Google's Nexus program is a bit of an understatement; I still have in my possession every single smartphone that bears the Nexus logo (I passed on the Nexus 10 tablet). I have always recommended a Nexus phone to anyone who asks, for the simple reason that every device sold is factory unlocked, even if purchased from a carrier with a subsidy.
And for Android modders like yours truly, Nexus phones are a realization of a future where smartphones are just like desktop PCs running Linux, commoditized black boxes where the user is free to install the distribution—Linux or Android—of their choice.
Until the OnePlus One I never seriously considered anything that wasn't
a Nexus; I ultimately passed on the OPO and stuck with the Nexus 5. In the case of the Nexus 6 I might well do the same.
I just don't think there's anything compelling enough about it to justify the price.