[SamAdams76]

Did you ever walk down the street and have somebody "nod" at you? What does that mean? Does that mean you have to nod back in order to be polite? If you do not return the nod, would you be considered to be rude?

Personally I do not nod back because I think that is some kind of homosexual communication.

[higgmeister]

Did you ever walk down the street and have somebody "nod" at you? What does that mean?

It is left over from the almost forgotten courtesy of tipping your hat.

[You tip your hat to this lady, son!   And when I did, all that hair fell out from underneath...]

The natural motion of tipping a hat involves nodding the head while reaching for the hat.

When hats became passé, the nod was the disconcerted leftover compulsion.