Back in the old days, it used to mean that a man was funny, but not physically attractive.
Today, it usually means that someone thinks the guy is a pervert. If you will recall he was in a “common law” marriage with Mia Farrow for 10 years. Mia Farrow adopted a bunch of children of her own, including a girl named Soon Yi Previn (Mia Farrow had been married to Andre Previn, so Mia Farrow and Andre Previn are Soon Yi’s legal adoptive parents) and then Mia Farrow and Woody Allen, who had been together for many years had a biological son, Satchel, together, and Woody and Mia adopted 2 other kids together Moshe and Dylan. So basically, for all intents and purposes, Woody Allen was the father figure, if not the legal step-father for all of Mia Farrow’s adopted children, as well as being the biological/legal father of Satchel and legal adoptive father for Moshe and Dylan.
For those of you keeping score, Soon-Yi Previn is the legal sister of Satchel, Moshe and Dylan, but because she was adopted, they are not blood related.
Anyoo, when Soon-Yi was 20 years old, and Woody Allen was in his late 40’s, it was discovered that he had been having a secret sexcual affair with her, even though he was still with (but not legally married to) Mia Farrow. Woody Allen and Soon-Yi Previn ultimately married each other.
Because he wasn’t married to Mia Farrow, apparently it was not technically considered to be incest, but because of the actual familial situation, and the fact that Allen’s 3 children with Farrow, are the legal siblings of Soon-Yi, it’s pretty gross and disgusting. (Hey look, Daddy’s having sex with our sister!) And the fact that he was sleeping with his girlfriend’s daughter is pretty disgusting too. And the fact that no one knows how long the sexual affair with Soon-Yi was going on before it was discovered, she might have been under-age when it started, and he was old enough to be her grandfather, which is kind of disgusting in it’s own sweet little way.
So either way, it’s not considered to be a compliment, but the first example is not nearly as bad as the second example.