Which word is synonymous with 'experienced without premeditation'?

The word that is synonymous with 'experienced without premeditation' is 'spontaneous'. This term refers to actions or events that occur naturally or without external planning or forethought. When someone acts spontaneously, they are responding in the moment, often based on their feelings or circumstances, rather than following a predetermined plan.

In contrast, the other terms suggest some level of planning or structure. 'Calculated' implies a deliberate and careful consideration before taking action, suggesting a planned approach. 'Arranged' denotes a sense of organization or preparation that contradicts the idea of spontaneous action. Similarly, 'structured' indicates a level of organization and formality, which does not align with the concept of acting spontaneously. Thus, 'spontaneous' is the correct choice, representing an immediate and unplanned response.