RG

RG may stand for:

Rg is the chemical symbol for roentgenium, element 111
renormalization group
Radio Guide, an obsolete US military standard still used to specify types of coaxial cable, see coaxial cable#Standards
Rio Group
the IATA code for Varig
Ragusa, Italy
renormalization-group methods
Slang for "Random Guy", as in this example: "I know everyone here but those two people by the window. Who are those RGs?"
Role Game, an abbreviation for RPGs.
Slang for "Relative grading". This word is a part of the lingo at all the IITs and IIMs. It has originated from the grading system of these institutes, where the students are graded in comparison to the performance of their peers. As a slang usage, it is meant for those people who would not help other people/hold on to important information/induldge in any deed that would harm other people (so that they relatively gain from it). Accusing of being an RG, is a matter of great dishonour.
It also refers to Windows RG, a parody of Windows ME in which RG sarcastically stands for "Really Good Edition."
The Direction centrale des renseignements généraux, the intelligence service of the French Police
Reachability Graph is a formal verification technique