primmest
prim-mest
adjective
The most excessively formal, proper, and easily shocked in behaviour or appearance.
"She wore the primmest dress to the casual gathering."
Thesaurus
Synonyms: victorian, prim, square-toed, strait-laced, proper, tight-laced, straitlaced, straight-laced, puritanical, straightlaced, priggish, prissy