deafinition
Refers to the assorted stipulations that determines if someone is completely hearing-impaired.
Different people have different deafinitions of hearing-loss... some unfortunates actually cannot hear anything at all, while others have a unique "selective" ear-disorder that only prevents them from hearing anything that's less-than-desirable (i.e., "The lawn needs mowing" or "It's you turn to do the dishes tonight"), but they can hear "welcome" remarks (i.e., "Dinner's ready" or "Let's have sex") perfectly fine.
deafinitely
So thunderously loud that it must be the case.
In "Chicago", sleazy defense-attorney Billy Flynn states that if you produce a loud enough roar during your lies-filled testimony of innocence, the jury won't be able to hear the truth above it, and so they will feel they have no choice but to just naively believe that what you say is deafinitely the case.