The complexityComplexity of systems is considered an invaluable information in the system developmentSystem development life cycle. While verificationVerification is a pervasive process also integral to system developmentSystem development, verification complexityVerification complexity is a rarely studied principle in systems engineeringSystems engineering. A lack of consensus on its definition causes limited attempts at measuring such complexityComplexity both in academia and industry. We propose a multifactorial verification complexity definition with the Verification Complexity Framework. Distinct verification complexity factors are stacked in layers, including verificationVerification design, structure, external factors, and information transfer across encapsulation levels. Each layer is then represented as a three-dimensional object visualizing multiple complexityComplexity aspects such as human factors and time. The framework is proposed to initiate discussion on the verification complexity definitions and its measures, aiming to provide a common mathematical vocabulary to the verificationVerification engineers in the field.