What is the meaning of Atomic?

Of or relating to atoms; composed of atoms; monatomic.

Employing or relating to nuclear energy or processes.

Unable to be split or made any smaller.

Containing a single change, as opposed to involving numerous unrelated changes.

Lacking logical operators; unable to be made simpler in logical form.

Such that for every element $b>0$ there exists an atom $a$ such that $b\geq a>0$ .

Guaranteed to complete either fully or not at all while waiting in a pause, and running synchronously when called by multiple asynchronous threads.

An atomic operation.

Source: wiktionary.org

See also