A sniglet is a neologism defined as "any word that doesn't appear in the dictionary, but should". Some examples of sniglets are:
Foodgitives: The food on one side of a TV dinner tray that escapes to the other side.
Furnidents: The indentations left in carpet after moving heavy furniture.
Glackett: The ball inside a can of spray paint (or other aerosol can) for stirring the contents inside the can. (This object is known as a "pea" in the paint industry.)
Pediddel: A car with only one working headlight (Hall 1984: 59) (Note: regional variant: Perdiddle)
Premblememblemation: Whenever you drop a letter in the mailbox, you always re-check to make sure it's gone down.
Pyramonster: That thing with one big eye on the back of a dollar bill. (The pyramid on the Great Seal)
Sniffleridge: The groove running between the nose and the mouth. (The real name for this structure is the philtrum.
Charp: The green mutant potato chip found in every bag.