"Instantly smitten" is a phrase that describes a sudden and overwhelming attraction or infatuation with someone or something. There are a plethora of synonyms one can use to convey the same meaning. A few examples include "love-struck," which emphasizes the intense emotions that can arise from being instantly smitten, "enamored," which implies a strong and lasting fondness, and "captivated," which describes a feeling of being completely absorbed or taken in by someone or something. Other alternatives include "head over heels," "infatuated," and "besotted," among others. Ultimately, the synonyms for "instantly smitten" depend on the context and level of intensity one wants to convey.