Nerf Dick 

A half hard/half soft penis

I was so drunk that I couldn't fuck that chick. All I could come up with was a nerf dick.

Nerf Dick by Big D Money September 20, 2007

Nerf dick 

A soft, small or unexpectedly small dick

John: fuck you
Bob: lick my balls
John: no your mom is already licking my balls

Bob: yeah she not sucking you dick because you have a nerf dick

Nerf dick by The man the myth the legend May 19, 2018