What to actually say
Open with this, more or less word for word: I was fired from that job, and I'd rather tell you that straight than dress it up.
It wasn't a layoff, it was a firing, and I'm not going to call it something else in this room.
Naming it in the first ten words removes the flinch that makes people think you're hiding something bigger.
The short version is I was hired to hit certain numbers, and after about eight months it was clear I wasn't going to, so they let me go.
One factual sentence gives them something concrete to hold, which stops them from filling in the blank themselves.
Since then I've taken on three contracts in that same area and closed two of them.
Forward motion after the fact matters more to most interviewers than the firing itself did.
I'd rather spend our time on what I'd actually do here than go back through what happened there.
It closes the topic without sounding like you're running from it, because you already answered directly.
How it usually goes
A version of the conversation with the push-back left in, because that is the part you need to have already heard once.
What not to say
It just wasn't the right fit.
Said alone it sounds like a cover story, and interviewers hear the gap where the fact should be.
My old manager had it out for me from day one.
Blaming a specific person, even accurately, makes the listener wonder what you'll say about them in a year.
So basically what happened was, over about six months, there were a few different things that built up and eventually...
A long wind-up before the point reads as guilt even when the content is fine, because length signals discomfort.
If they ask whether it was 'for cause' or what specifically you did wrong
Don't match their specificity with more of your own just to seem cooperative. Give the category, not the file. Say: 'It came down to performance, not conduct — nothing you'd need to worry about with a background check or a reference call.' That sentence answers the actual question underneath their question, which is usually 'is this person going to be a problem,' without you narrating the meeting where you were let go. If they keep pushing past that, it's worth noticing what kind of place asks twice.