Definitions of image schemas have generally been found to be underspecified in image-schematic literature, which is particularly true for the image schema VERTICALITY. A frequently adopted approach to address this issue is to provide formal definitions. The use of image schemas in natural language is one central source of evidence for their existence, but spatial language is highly flexible and rarely contains explicit disambiguated spatial information. Thus, applying formal definitions that require non-linguistic spatial properties for the annotation of linguistic manifestations of image schemas is problematic. In this paper, we propose an interdisciplinary review of definitions and suggest annotation guidelines for the image schema VERTICALITY in natural language, including an annotation experiment with three experts.