pencil dick

noun2

1. •
   (vulgar, offensive) A penis of inadequate girth.

   • Big fat cocks are way too much for my butt; long and thin is in (me). If you've got above average length and average girth I've got the rubbers and lube. — 1991
2. •
   (vulgar, offensive) A man with a penis of inadequate girth.

   • “When's the last time I asked you to do anything for me, pencil dick?” — 2010