Dictionary.com gives this definition:
1. belonging to the Pinnipedia, a suborder of carnivores with limbs adapted to an aquatic life, including the seals and walruses.
Ah, the Pinnipedia! Try dropping THAT vocab gem into a conversation today. When confronted with the inevitable "Pinna-what?" don't give them the satisfaction of an answer. Instead, try raising your eyebrows and saying in an amused tone, "Really?" then, when they don't answer, look around to the others in the conversation and mouth the word "WOW." You can follow up with a dismissive "Any-waysss."
Let me know how it goes.