1. a deceptive, misleading, or false notion, belief, etc. expressed for the benefit of one's penis
2. a misleading or unsound argument supporting an act which would be pleasurable for one's penis
3. deceptive, misleading, or false nature regarding one's penis, esp. size; erroneousness in relating facts regarding one's penis
4. In logic: any of various types of erroneous reasoning that render arguments supporting an act which would be pleasurable for one's penis logically unsound
He boasted that he was well-endowed, and this became a commonly believed phallicy.
He said he loved her, but it was only a phallicy.
All of his former hook-ups accused him of phallicy.
The most commonly used phallicy the fourth kind is "Everybody's doing it."