1. The top half of a bun, or top layer of bread on a sandwich. Often used to refer to the thickness of the bun or bread.
The term "top bun" is often used to describe the amount of bun on the top layer of a sandwich or burger. The person often uses this term in displeasure of the thickens off the bun; often seek approval or acknowledgement that their bun is to thick.
eg: Person 1: "look at the amount of top bun I have, its to much"
Person 2: "Its fine"
Person 1: "No its not fine, I refuse to eat this. There is to much top bun!"
Refusal to acknowledge the top bun may results in refusal to eat the meal, until the amount of top bun is noted.