Three-letter acronym (ConceptClass, 3)
From Compile Worlds
A three-letter acronym, otherwise known as a TLA which is itself a three-letter acronym, is (surprise surprise) an acronym with three letters in it (or in some cases, numbers or other characters). It's often suggested that the most important acronyms are TLAs, in fact, they're apparently so important that even Wikipedia needs an article about them.