Approximation adjectives are listed in this post. Each word below can often be found in front of the noun approximation in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing APPROXIMATION.
above, acceptable, accurate, adequate, asymptotic, best, better, born, certain, close, closer, closest
constant, continuous, convenient, crude, decimal, discrete, distant, enough, excellent, fair, field, first
further, gaussian, general, good, gradual, greater, harmonic, initial, less, linear, local, mere
mutual, near, nearer, nearest, new, next, normal, numerical, only, order, polynomial, poor
possible, practical, quadratic, rational, reasonable, remarkable, rough, rude, same, satisfactory, second, simple
slight, successive, such, sufficient, third, tolerable, useful
Hope this word list had the adjective used with approximation you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.