Real Dictionary

brat
countable noun: If you call someone, especially a child, a brat, you mean that he or she behaves badly or annoys you.

brat in American English
a child, esp. an impudent, unruly child
noun: a child, esp. an annoying, spoiled, or impolite child (usually used in contempt or irritation)

brat in British English 1
noun: a child, esp one who is ill-mannered or unruly: used contemptuously or playfully

brat in British English 2
noun: an apron or overall