As used in physics, the term "exact" generally refers to a solution that captures the entire physics and mathematics of a problem as opposed to one that is approximate, perturbative, etc. Exact solutions therefore need not be closed-form.
Exact Solution
See also
Closed-Form Solution, ExactExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Exact Solution." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ExactSolution.html