Noun
(sciences, strictly) A mathematical science, i.e. a field of science such as mathematics or mathematical physics which is capable of perfectly exact results based on rigorously formal methods.
(sciences, broadly) A field of science such as physics or chemistry that is not perfectly exact, but still capable of highly quantitative results based on methods that are are not strictly rigorous, but still systematic and scrupulous.
(litotes, chiefly in the negative) Used contrastively to characterize something as imprecise or relying on intuition or heuristics.
Jury selection isn't an exact science.
Although this may seem a paradox, all exact science is dominated by the idea of approximation. When a man tells you that he knows the exact truth about anything, you are safe in inferring that he is an inexact man. Bertrand Russell
An exact science is one that admits loss. Genesis P-Orridge
The subjective element in geological studies accounts for two characteristic types that can be distinguished among geologists. One considering geology as a creative art, the other regarding geology as an exact science. Reinout Willem van Bemmelen
Economics is not an exact science. John Kenneth Galbraith
but, in reality, there is no such thing as an exact science. William Stanley Jevons
Hitting is an art, but not an exact science. Rod Carew