1. Description of a word formed from the first (or first few) letters of a series of words; as with radar, which comes from radio detecting and ranging; NATO, which comes from North Atlantic Treaty Organization; scuba, which comes from self-contained underwater apparatus; and sonar, which comes from sound navigation ranging.
2. Characteristics of words created from the initial letters of a phrase; for example, "Random Access Memory" becomes RAM, pronounced as the word "ram"; and the scientific term LASER is a result of "Light Amplification by Stimulated Emission of Radiation".