Travel Security Glossary

Short, standalone definitions (under roughly 150 words) of terminology travelers encounter but don't fully understand: 3-1-1 rule, dual-use item, Secure Flight, watt-hours (Wh), minimum connection time (MCT), personal item vs carry-on, TSA PreCheck. Boundary: definitions only; full reasoning, checklists, and citations for the underlying rule live on the linked tsa-rules or airport page, not here. Directly serves "what is X" query patterns.