"The conversational overachiever is someone whose grasp exceeds his reach. This is possible but not attractive"

This quote by Fran Lebowitz is describing someone who talks too much and too confidently about topics they do not in fact comprehend. This person might be attempting to appear more knowledgeable than they in fact are, but this behavior is not attractive. It is possible to have a greater understanding of a subject than one can actually demonstrate, but it is not a desirable trait. This quote is a pointer to be truthful and humble about what one knows and to not attempt to overcompensate for a lack of knowledge. It is much better to be honest and confess when one does not understand something than to try to bluff their method through a conversation.