There are a large number of great words that you never see in dictionaries (not even in the large, expensive ones; the ones with words between fuchsia and fucus). I used one today in another post and thought that this imbalance should be redressed. I invite anyone else that knows some welcome additions to the english language (that the likes of Oxford and Webster have sadly overlooked) to post them here.
Here's a few to kick things off. I have limited myself to the more tasteful examples that I can think of!
Bellywash (n) - cheap, low-alcohol beer.
Brainfart (n) - a temporary mental aberration.
Cribvirgin (n) - someone whose first post in a forum is an attempt to get someone else to write their essay / dissertation / course work.
Elton (n) (vt) - the word in a song that you are singing along to that is completely different to the one you actually sang. To sing this word.
Gamlin (n) - the act of getting one's partner's name wrong in bed.
Klint (n) - the croaky tone of voice adopted when ringing into work sick.
Ludlow (vi) - to speak very loudly on public transport whilst wearing headphones.
Milton (n) - a person that still gets asked their age when buying alcohol, even though they are over 30.
Phubb (n) - The sound of an obese person passing wind on a plastic chair.
Quilson (n) - the state of somebody's hair immediately after removing a hat.
Preantepenultimate (adj) - fourth from last.
Vernon (n) - a person that comes and talks to you through the door at a party when you are in the bathroom being sick.
Zankle (n) - the overwhelming desire to bite into a new bar of soap.
Any further examples will be gratefully received.