noun
club activities; extracurricular activities
Refers to school-based club activities, often after school. Synonymous with the shorter 部活 (ぶかつ), which is more casual.
See also: 部活
高校では部活動に参加する生徒が多い。
Many students participate in club activities in high school.
部活動の時
Club activity time starts at 4 p.m. every day.
Often refers to university-level clubs or hobby circles, which may be less formal than school 部活動.
Compound of 部 (ぶ, 'club') + 活動 (かつどう, 'activity'). The exact historical derivation is straightforward; the word is a modern term for school club activities.