When your dick is so dank it smells like sulfur and/or tastes like sulfur. Often developed through poor hygiene or sweat from busting your ass after a long hard day of work.
Boyfriend: Baby I know I worked all day but I need a blow job.
Girlfriend: Okay Daddy let me get that dick.
Boyfriend: Takes dick out and BAM!
Girlfriend: ewww babe you have sulfur dick.