RAT

Remote Access Technician
Ram air turbine
Ram Air Temperature
Radio access technology
Register Alias Table
Remote Administration Tool
Remote access terminal
Rider's Association of Triumph
Release after transmission (Token ring)
Rock Abrasion Tool of the MER-A (Spirit) and MER-B (Opportunity) Mars rovers
Rough and Tumble - a martial art of South African origin

Translation

The word "RAT" occurs as such in the following languages: English, Esperanto, Italian, Japanese.