wisdom tooth
countable noun: Your wisdom teeth are the four large teeth at the back of your mouth which usually grow much later than your other teeth.
wisdom tooth in American English
the back tooth on each side of each jaw in human beings; any of the four third molars appearing usually between the ages of 17 and 25
noun: the third molar on each side of the upper and lower jaws: the last tooth to erupt
wisdom tooth in British English
noun: any of the four molar teeth, one at the back of each side of the jaw, that are the last of the permanent teeth to erupt