expression, adverb
especially; exceptionally; remarkably; conspicuously
Used to single out something as standing out from others in degree or quality. Often modifies adjectives or verbs to emphasize a notable difference.
今年の夏は突出して暑い。
This summer is exceptionally hot.
彼はクラスの中で突出して成績が良い。
He has remarkably good grades in the class.
From the verb 突出する (to protrude, to stand out) in its て-form, used adverbially. The kanji 突 means 'thrust' or 'protrude', and 出 means 'come out', together suggesting something jutting out and thus being conspicuous.