godan verb (-u)
exchange ideas vigorously; have a lively debate; clash opinions
Used for a spirited exchange where people present competing ideas, often in meetings or discussions. The focus is on the dynamic interaction, not physical collision.
会議では、参加者が自由に意見をぶつけ合った。
At the meeting, the participants freely exchanged their opinions.
彼
They bounced ideas off each other and came up with a better plan.
godan verb (-u)
crash into each other; smash together; throw at each other
Physical collision or throwing objects at each other. Often implies a mutual, sometimes chaotic action.
子供たちは雪玉をぶつけ合って遊んでいた。
The children were playing by throwing snowballs at each other.
二台の車が正面からぶつけ合った。
The two cars crashed into each other head-on.