Imagine you are taking part in a heated discussion at work, and all of a sudden, one of your colleagues forcefully interrupts the conversation in order to assert their opinion. When someone aggressively enters a conversation, debate or discussion without waiting for their turn, you can describe their behaviour with the idiomatic expression entrare a gamba tesa.
entrare a gamba tesa
to do something in a confrontational way

Entrare a gamba tesa literally translates to “to enter with a stretched leg.” It evokes the image of someone forcefully stepping into a situation, often with a noticeably lack of subtlety. As you might expect, this expression is frequently used in business contexts or situations where meetings involve individuals with differing opinions.
Durante la riunione, il capo è entrato a gamba tesa, criticando il nostro lavoro.
During the meeting, the boss forcefully intervened, criticising our work.
Scusate se entro a gamba tesa, ma vorrei ricordarvi che la scadenza per consegnare il progetto è molto vicina: dobbiamo sbrigarci!
Excuse me for barging in, but I would like to remind you that the deadline for delivering the project is very close: we need to hurry!

In the world of soccer, entrata a gamba tesa (also known as fallo a gamba tesa) refers to a specific kind of tackle called a studs-up tackle. You can see a video of it here, and I have to say, it looks rather painful!
Heather Broster is a graduate with honours in linguistics from the University of Western Ontario. She is an aspiring polyglot, proficient in English and Italian, as well as Japanese, Welsh, and French to varying degrees of fluency. Originally from Toronto, Heather has resided in various countries, notably Italy for a period of six years. Her primary focus lies in the fields of language acquisition, education, and bilingual instruction.