1.NounThe use of a sound or form that is perceived as foreign in a context where a native sound or form would be more correct based on the original language of a given loanword.
"When he wrote that he was going to “Hämbürg”, it was considered a hyperforeignism because the German form is “Hamburg”.; Although most hyperforeignisms are accidental, there are some intentional ones, such as Target being humorously called "Tarjay.""
2.NounThe misapplication of foreign pronunciation or usage more broadly; approximation that is misapprehensive or pedantic; use of a foreign form that is not in common use.
"When she talked about the beautiful “freschi”, this was considered a hyperforeignism because in English the plural form “frescoes” is used."