muff2 [transitive] informal
1 also muff something ↔ up
to spoil a chance to do something well or achieve something:
You'll probably only get one chance to take a photo, so don't muff it!
to fail to catch a ball or kick it properly in a game or sport:
With only the goalkeeper to beat, he completely muffed his shot.
3 British English
if you muff your lines in a play you are acting in, you forget them or say them wrongly