a large forehead

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

An abnormally large forehead.

While the forehead is defined as the part of your face above the eyebrows to your hairline, a fivehead is ascribed to someone that has a rather large forehead.

A forehead so incredibaly large it can be classified by the next number up.

A very large forehead - 25% larger in fact.

When some one has an extremely large forehead.