An old woman typically between the ages of 70-90 that is commonly seen on news channels for accidentally crashing their cars into shopfronts. A standard Sheggy is an old women with grey/white curly hair and a pre-2000s car generally ranging from the colours white, blue, gold tint and silver.

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.

its a scottish slang for something is shit.

When a person thinks they are big and own the shot.
Usually refers to a man that owns a suped up car and thinks they are a boy racer.
Also refers to a guy that refers to their mate as sheg.