Any person who, literally or figuratively, aggressively tries to wrap their cock hungry lips around a dick.
Literal usage isn’t hard to imagine:
You are making out with your girlfriend, and surprisingly quickly her, lips start tracing down your treasure trail
and before you know it, she has your dick in mouth - d.i.m
“Oh Veronica, you little dick shark”
The gay guy at a club is really going after some cock:
“Look at Jesse up at the bar hitting on that tall, handsome Dutchman - total little dick shark”
Your 35-year old, single, female, career-driven boss hasn’t been on her back in months, and at the office party:
“Look - Lisa keeps brushing Craig’s belt buckle while they chat it up.” “Yeah, she’s being a real dick shark.”
Figuratively, it means anyone who is sucking up, or using sexual appeal to get ahead:
“The clients came to town and Ian was a total dick shark – couldn’t get their zippers open fast enough.”
“Tina’s nervous about the re-organization – nothing but the boss’s cock in her mouth will calm that little dick shark down.”
One last twist is to use it as a fake name.
The parts counter clerk barreled – “So you think this is warranty, ehh, well step on into Dick Shark’s office, and you two can straighten it out”