Is vesicle the proper medical terminology for pimple?

No, "vesicle" is not the proper medical terminology for a pimple. A pimple is commonly referred to as an "acne vulgaris" lesion, which is an inflammatory condition of the skin caused by the overproduction of sebum. Medically, a small, elevated, circular skin lesion filled with fluid or pus is referred to as a vesicle, while a pimple is a specific type of inflamed or infected sebaceous gland unit on the skin.