talk trash
US /tɔk træʃ/
UK /tɔk træʃ/

1.
hablar mal, provocar, fanfarronear
to speak badly or insultingly about someone or something, often in a boastful or provocative way
:
•
He always talks trash about his opponents before a game.
Siempre habla mal de sus oponentes antes de un partido.
•
Don't talk trash if you can't back it up with your actions.
No hables mal si no puedes respaldarlo con tus acciones.