prefix
vigorously; suddenly; with force
Emphatic verbal prefix used before verbs to add a sense of doing something vigorously, suddenly, or with force. Common in colloquial and informal speech. Often written in kana.
彼はおっ走って教室を出ていった。
He suddenly dashed out of the classroom.
おっかぶせるように布団をかけた。
I threw the blanket over him vigorously.
Similar emphatic prefix, but ぶっ often carries a more violent or forceful nuance (e.g., ぶっ飛ばす). おっ is slightly milder and more sudden/vigorous.
Derived from the emphatic prefix 押し (oshi) or 追い (oi), contracted to おっ before certain verbs. The exact historical derivation is uncertain, but it functions as an intensifier in modern colloquial Japanese.