noun ( NAmE , informal )
1.
a person or thing that you are annoyed with :
My car's at the shop—the son of a gun broke down again.
2.
used to express the fact that you are surprised or annoyed :
Well, son of a gun—and I thought the old guy couldn't dance!
3.
( old-fashioned ) used by a man to address or talk about a male friend that he admires and likes :
Frank, you old son of a gun—I haven't seen you for months.