The general meaning of "atomic" is "irreducible". That is, reduced to the smallest possible part. It has more specific meanings in several contexts:

• In chemistry, chemical atoms are grouped by type in the periodic table and consist of particles as described by particle physics.
• In computer science, an atomic operation is one that cannot be subdivided. Or more specifically, an operation that always completes as a whole, or doesn't complete at all. See atomic (computer science).
• In order theory an atom is an abstract generalization of a singleton set in set theory and an atomic element provides an abstract generalization of the ability to select an element from a non-empty set.
• Atomic is an Austrian ski producer.
• "Atomic" is the name of a song by the rock band Blondie.
• Atomic is also an Australian computing and technology magazine.