dirty old man

noun, Informal.
1.
a mature or elderly man with lewd or obscene preoccupations.
Origin
1930-35
Slang definitions & phrases for dirty old man

dirty old man

noun phrase
  1. A lecherous man, esp an elderly one; old goat (1930s+)
  2. A male homosexual whose partner is much younger than himself: Christopher is 20 years younger than Leo. He asks Leo to be his dirty old man (1960s+ Homosexuals)