What Does 5s and 20s mean? 

Branches: All.

Definition: In the military, this refers to checking the five-metre radius, and then the 20-metre radius so that one has a complete idea of their immediate surroundings. It can also refer to someone who’s got a keen observation of their environment.

Example: The relationship was exclusive and we were heading in the right direction, but I soon realised that the person I was with was more interested in the hookups they found in their 5s and 20s.