a large, disorderly crowd of people, especially one that may become violent or cause damage.

多数の人の集まり・群衆（特に秩序を乱したり暴力を振るったりする可能性のあるもの）

informal: organized crime groups collectively (especially the Mafia) — often used with the definite article 'the'.

（口語）組織犯罪集団（特にマフィア）

to gather around or attack someone or something in a large, disorderly group; to crowd round aggressively.

（人が）押し寄せる、群がる、襲いかかる

informal (often online): to subject someone to a large-scale collective attack or criticism (e.g., public shaming or harassment).

（特にネットで）多数で攻撃する、集中して非難する