The software testing technical terms - not only for ISTQB® Certified Tester Download PDF

1. An approach to testing whereby the testers dynamically design and execute tests based on their knowledge, exploration of the test item and the results of previous tests. [Reference: After ISO 29119]

2. experience-based testing in which the tester spontaneously designs and executes tests based on the tester's existing relevant knowledge, prior exploration
of the test item (including the results of previous tests), and heuristic "rules of thumb" regarding common software behaviours and types of failure.
NOTE: Exploratory testing hunts for hidden properties (including hidden behaviours) that, while quite possibly benign by themselves, could interfere with other properties of the software under test, and so constitute a risk that the software will fail.