To an unusual, remarkable or exceptional degree.
"The storm was exceptionally fierce, tearing roofs off houses and knocking down entire trees."
In plain English: Exceptionally means something is done to an extremely high degree, far better than usual.
"The weather was exceptionally cold this winter morning, so I wore three sweaters to stay warm."
Usage: Avoid using "exceptionally" as a synonym for "very," which can sound redundant; instead, reserve it for situations that truly deviate from the norm. It often carries a slightly more formal tone than intensifiers like "extremely."
Exceptionally comes from adding the suffix -ly to exceptional, which itself is derived from Latin meaning "outside the rule." The word entered English through French and originally described things that fell outside normal limits before evolving into its current use for extreme degrees of a quality.