a posteriori

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Derived by or designating the process of reasoning from facts or particulars to general principles or from effects to causes; inductive; empirical.
• adjective Justified by appeal to experience.
• adjective Knowable from experience.

from The Century Dictionary.

• noun Literally, from the latter or subsequent; hence, in logic, from a consequent to its antecedent, or from an effect to its cause: used of reasoning which follows this order, formerly called demonstratio quia, or imperfect demonstration.

from the GNU version of the Collaborative International Dictionary of English.

• (Logic) Characterizing that kind of reasoning which derives propositions from the observation of facts, or by generalizations from facts arrives at principles and definitions, or infers causes from effects. This is the reverse of a priori reasoning.
• (Philos.) Applied to knowledge which is based upon or derived from facts through induction or experiment; inductive or empirical.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective logic Involving deduction of theories from facts.
• adverb logic In a manner that deduces theories from facts.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective requiring evidence for validation or support
• adverb derived from observed facts
• adjective involving reasoning from facts or particulars to general principles or from effects to causes