You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
FA_Cup

Context:
The possibility of unlikely victories in the earlier rounds of the competition, where lower ranked teams beat higher placed opposition, known as "giant killings", is much anticipated by the public, and is considered an integral part of the tradition and prestige of the competition, alongside that gained by teams winning the competition. Almost every club in the League Pyramid has a fondly remembered giant-killing act in its history. It is considered particularly newsworthy when a top Premier League team suffers an upset defeat, or where the giant-killer is a non-league club, i.e. from outside the professional levels of The Football League.

Question:
What is a giant killer? 

unlikely victories in the earlier rounds of the competition, where lower ranked teams beat higher placed opposition