A verbal mistake; saying words incorrectly (essentially the same as 'slip of the tongue').
彼のスピーチにはいくつか言い間違えがあった。
There were a few verbal mistakes in his speech.
録音を聞くと、いくつかの言い間違えに気づいた。
Listening to the recording, I noticed a few slips of the tongue.
言い間違えに気づいたらすぐ訂正したほうがいい。
If you notice a verbal mistake, it's best to correct it immediately.