Verification: Confirmation through examination of a given item and provision of objective evidence that it fulfills specific requirements. Comparing an activity, a process, or a product with the corresponding requirements or specifications.
Verification = Theoretical (the old "According to my calculations...")
Validation = Actual as determined by testing (often done on a prototype, but in some cases validation is done through actual use - depends upon the product and the industry).
Note: Not to be confused with calibration of a measuring system as described in the below links.
Elsmar Cove discussion threads related to Calibration Verification:
Definition of Calibration from ISO/IEC 17000
Calibration vs. Verification - A Good List of Definitions
Calibration vs. Verification - ANSI/NCSL/Z540 - Definitions of
Calibration vs. Verification - Definition of
Verification vs. Validation vs. Calibration - What is the difference?
Calibration? Verification? Is this a calibration?
What is the difference between in house calibration and verification?