What is Petus?
1.
Petus is a term for a full-grown male who has a penis so small it could be the penis of a fetus.
"That guy showed me his penis in the bathroom. It was so small I'm sure it was a petus."
See
2.
Alternative to penis... also can be an insult
AHH! She bit my petus.
Bob, quit being such a petus