The word 'goof' is especially used in America and mostly it finds its use in the informal conversation. The meaning it conveys is that of a stupid mistake. The following sentence can make the meaning quite clear: Sorry boys, I goofed. In the abovementioned sentence the person is apologising because he made a mistake.
In the abovementioned sentence the word is used as a verb but it can be used as a noun as well and conveying the same idea. But in addition it is also used for the person who made the mistake.
The word can also be conjugated with 'around' and 'off' to form phrasal verbs. If you are spending time doing silly things you are goofing around and also when you are doing nothing when you have important things to do you are goofing off.
In the abovementioned sentence the word is used as a verb but it can be used as a noun as well and conveying the same idea. But in addition it is also used for the person who made the mistake.
The word can also be conjugated with 'around' and 'off' to form phrasal verbs. If you are spending time doing silly things you are goofing around and also when you are doing nothing when you have important things to do you are goofing off.