gang up on or against someone Definition

gang¹
noun

1. A group, especially one of criminals or troublemakers.

Thesaurus: group, crowd, pack, circle, clique, ring, coterie, mob, club, party.
2. A group of friends, especially children.
3. An organized group of workers.
4. A set of tools arranged so as to be used together.

verb

ganged, ganging
1. To arrange (tools) for simultaneous use.

Etymology: 17c in senses 1 to 3; 14c in sense 4; from Anglo-Saxon gong a journeying.

Phrasal Verb: gang up on or against someone

To act as a group against them.

Phrasal Verb: gang up with someone

To join in or form a gang with them.