Abstract Purpose Previous discussions have characterized hookup culture as ambiguous by nature, but social psychological theory tells us people dislike ambiguity in practice. Meanwhile, a myriad of undefined relationship terms (e.g., talking to, hanging out, having a thing) arose and have remained in use. I examine (1) whether these different “situationship” labels have distinct affective meaning and (2) what that suggests for those occupying the concomitant identities (i.e., assess the behavioral and emotional consequences of being “someone in a _____ relationship”). Approach Using affect control theory and a sample of young adults in defined (N = 50) and undefined (N = 43) relationship types, I test if affective ratings of various relationship label identities are statistically distinct. I then computationally model social events with each relationship label as actor (X identity performs [behavior]), compare their differing levels of social discomfort, and empirically predict the emotions each identity would feel. Findings Undefined relationship labels are not synonymous. Correspondingly, the nature, emotions, and expected behaviors of the individuals with those labels' related relational identities are not equivalent. In cultural evaluation, all undefined relationship labels are lower than all defined relationship labels. In event simulations, predicted deflection levels and actor consequent emotions (how normative is it and how jarring does it feel) were patterned by the labels' cultural evaluation ratings, these correlate with relationship commitment level. Implications By interpersonal necessity, individuals make fine distinctions in shared meanings within a cultural context of constant redefinition. Physically and emotionally negative behaviors are culturally more expected and accepted in undefined contexts by the culturally-understood nature of – and shared perspectives of participants concerning – those relationships’ parameters.