Making nylon

(Verb) Masturbating (male) in the bath.

Wilburrrrrrr! Hurry up out of the bathroom; I want a shower. You'd better not be making nylon in there...

Umfriend

Noun; a person with whom one's relationship is ill-defined, illicit or uncertain.

This is Xxxxx. He's my umfriend.
(Not to be confused with "unfriend", verb; to remove a person from one's list of "friends").

BORC

Acronym; a large box or bag housing items which are perfectly serviceable, and which the owner fools himself may become useful.
BORC - Box Of Random Crap.

Have you got a lead with the correct plugs to charge my 3 year old phone?
Probably; try looking in the BORC.

Fartapeutic index

-(noun)-with ref to sugar-alcohol-based artificial sweeteners; The difference in quantity between enough to result in the proband's uncontrolled production of foghorn-volumed flatulence, and the quantity which results in his making fizzy gravy.

Fartapeutic index of erythritol-high; FI of maltitol- dangerously low. Empirical data re the latter are published within the Amazon customer reviews of "sugar free jelly bears", the conclusion of the most authoritative of which reads "Jesus, my poor ringpiece".