(chemistry) any theory in which all matter is composed of tiny discrete finite indivisible indestructible particles; "the ancient Greek philosophers Democritus and Epicurus held atomic theories of the universe"
(psychology) a theory that reduces all mental phenomena to simple elements (sensations and feelings) that form complex ideas by association
confidently aggressive; "too assertive as a salesman"; "his self-assertive and unflagging energy"
inclined to bold and confident assertion; aggressively self-assured; "an energetic assertive boy who was always ready to argue"; "pointing directly at a listener is an assertive act"
completely neat and clean; "the apartment was immaculate"; "in her immaculate white uniform"; "a spick-and-span kitchen"; "their spic red-visored caps"
marked by excessive confidence; "an arrogant and cocksure materialist"; "so overconfident and impudent as to speak to the queen"; "the less he knows the more positive he gets"