aka: someone who doesn't give up until their point has been made, or until they get what they want. Usually someone who is very stubborn.
Melissa: Nooo! It's so funny!
Rebecca: MELISSA DELETE THIS NOW. Am I going to have to be a PLB on your ass?
"Don't be such a PLB!"
The term is also applicable in everyday life for a person who flakes out on fun activities for unknown or unjustified reasons.
Nick: HAHAHA, I'm watching my lane!
Jim: What a PLB
Ben: John, are you in for this game of Beer-Pong?
John: Hold on, I'm playing with this scorpion I just found.
Ben: Get your ass over here, ya prancin' little bitch, The team needs you!!