SMIDSY

Etymology
Acronym for "Sorry mate, I didn't see you."

Phrase

 * 1)  Sorry mate, I didn′t see you.

Noun

 * 1) An accident in which a larger vehicle hits a motorcycle or bicycle because the driver did not see the cyclist.

Usage notes
The acronym is used by motorcyclists and cyclists in reference to traffic collisions in which the driver of a car or larger vehicle claims not to have noticed a two-wheel biker. It is usually derogatory, in that the claim is often that the driver was not at fault (when they patently were).

A related usage by the UK government is.