In today's Family Guy episode, called Seahorse Seashell Party, when Meg was complaining to her mother Lois, her father Peter came to her and whispered something in her ear. Then Meg said:
Meg: (complaining) And you never let dad stir the paint anymore, whatever that means.
Peter: I didn't know you knew that, Meg, but I'm glad you brought it up.
Any idea what does the phrase mean? I guess it's sex-related, but I'm not 100% sure.
So far the answers say that the phrase means to have sex while the woman is menstruating. This sounds plausible and fits, but the answers are backed up by the entry in the Urban Dictionary, which was created right after the Family Guy episode aired. Therefore, I assume people simply guessed what the phrase means and submitted it to the Urban Dictionary and thus I don't consider it to be a reliable source in this case.