Part 1. Definition
Given a prompt and two completions from a language model, select the completion that is the most fluent with respect to continuing the prompt. Fluency is defined by coherency and ease of understanding, not necessarily grammatical correctness. Generate either Completion A or Completion B.
Part 2. Example
Prompt: Im 99 percent sure it was someone being an 
Completion A: accomplice , or maybe just plain old con man . whatever it was , it 's over . " 
Completion B: asshole, your right?) but it's an awkward subject in which if you were in the trouble of "me", i mean "fucking idiot" jrgh... i dunno...I guess you are (in a legal context) not a stupid
Answer: Completion A
Explanation: This prompt-completion pair is more fluent because it is more easy to follow and is a realistic statement.
Part 3. Exercise
Prompt: Sometimes the shit you fuck with, is just 
Completion A: shit.  And the stuff you do is not only fuck, but also fuck shit, or at least fuck shit like that. Fuck your own 
Completion B: plain nuts. You are trying to turn this into something to talk about. Your attitude is like that of an off ramp driver. So far, s
Answer:
Completion B