A space between a girl's upper thighs that can be seen when she is standing if she is thin. This is often an excellent indicator of the rest of the girl's body, as if a girl has upper thigh clearance (or, for short, "UTC") then she is likely thin everywhere else. Absent upper thigh clearance, you are taking a risk that she's a chubster. Note: This phrase is also referred to as "inner thigh clearance"

No Bull Shit, and old hacker acronym which is usually used to signify that the talk will be serious.