What is Baby On Board?
1.
a stupid freaking yellow sign that most commonly mothers put on their car window to signify the fact that a baby is "in the car" Which basically means drive carefully which you should be doing anyway and who cares? Good on you for having a baby, you dont have to share it with the world because surprisingly no one else cares.
Franz: "Oh look, those people have a baby on board, i can tell by that yellow sign that hangs in their window."
Citronella: "How stupid, what are we meant to do? Drive slower? Donate some money? Beep our horn? What are they trying to prove. Friggen idiots."
Franz: "Citronella you are perfectly right."
See
2.
A sign that can often be seen in car windows indicating that a baby is riding in the car.
Popularized in the simpsons episode where Homer joins the B Sharps, and makes these 3 words into a song.
The Song:
Baby on board,
how I adore,
that sign in my car windowpane.
Folks stop and stare, friends I don't care
That little yellow sign can't be ignored
I'm telling you it's mighty nice
Each trip's a trip to paradise
With my baby on board.