Small Penis Mobile 

A jacked up 4 wheel drive pick up driven by someone who thinks they're much cooler than they really are (see punk-ass bitch), often coupled with an over-sized ego, which both are used to compensate for an abnormally small penis.
Small penis mobiles are often complimented by a Calvin pissing or "Cowboy Up" sticker in the back window.

I heard that dude that drives that small penis mobile got beat up by his little sister.

Small Penis Mobile by Howie Feltersnatch January 1, 2004

Small Penis Mobile 

Hummer H2

restore your manhood

The Hummer H2 is the most popular small penis mobile

Small Penis Mobile by Angelino August 14, 2007

Small Penis Mobile 

Any vehicle modified to stand out, whether by size, muffler noise, stereo, wheels, tinting, or stripes, so as to create the illusion of manhood and self worth in the midst of a pointless insecure primal existance. Size and noise are the default mediums whereby those who have nothing to offer themselves or society can protest their own ignorance as if it were someone else's fault.

I heard a loud muffler followed by screeching tires and turned to see the small penis mobile.

Small Penis Mobile by John Phillips April 19, 2006