Typically used as a defense when such people fail to answer a multi-part equation, and don't feel like admitting their mistake.
When a person uses this term they are basically saying that there should have been brackets surrounding certain parts of a math equation.
Person 2: 20!
Person 3: No it's 14, learn your order of operations.
Person 2: No! It's supposed to be read as "(2 + 3) x 4". Implied Parenthesis noob!
Person 3: If that were true then the entire order of operations would be untrue.
Person 2: IMPLIED PARENTHESIS!!!11!