someone who annoys you because they think that they know more about a particular thing than anyone else
Origin and usage
The noun wiseacre comes from a Dutch word meaning ‘soothsayer’. It was first used in English in the late 16th century.
Although it is known that wiseacre comes from a Dutch word, ‘wijsseggher’, it is not clear why the second part became ‘acre’ rather than, say, ‘sayer’. Perhaps it was a similarity in the sounds that led to it being misinterpreted. The spelling wiseacre was established early on, although the word was sometimes hyphenated and sometimes spelled with a ‘k’. Wiseacre is not a commonly used word nowadays, occurring only 300 or so times in the large corpus we use when compiling Macmillan Dictionary. To me it has a somewhat old-fashioned and folksy feel. English is rich in words for people who like to show off their knowledge, however; you can explore them here.
“The wiseacres failed to understand something very simple: stumbling is not falling, as Malcolm X said.”
“Some wiseacre has placed it on record that too much of a good thing is worse than none at all.”
know-all, wise guy, smart alec