Slang someone of impressive ability and daring, specially a person who is very successful and self-assured.
A nonstop freight train.
somebody with exceptional skills in a specific area.
an effective, self-confident one who is regarded by other individuals as highly skilled; -- sometimes used ironically in mention of the intense persons whoever opinion of one's own talents is regarded as exaggerated.
A foolish, inconsiderate other.
someone who is dazzlingly competent in virtually any area