off on a rant 意味

• 《be ～》熱弁｛ねつべん｝を振るう
  

• rant:    rant v. わめく, どなり立てる.【副詞２】He ranted on for twenty minutes. 20分もわめき続けた.【＋前置詞】He began to rant about the number of immigrants in the country.国内の移民の数について大げさに言い立てはじめたShe was ranting against the moral dec
• rant on:    わめきちらす
• foulmouthed rant:    口汚い暴言｛くちぎたない ぼうげん｝

例文

1. all you had to do was mention the bunsen burner and he was off on a rant .
   ブンゼンバーナーと 言うたびに大騒ぎだ