Boxeador vs. pugilista
In Portuguese, both boxeador and pugilista refer to a boxer. They are essentially synonyms and are often used interchangeably in Brazil and Portugal. The main difference lies in their etymology and tone: boxeador is the direct derivative of the sport boxe (boxing), while pugilista has Latin roots and can sound slightly more formal, technical, or journalistic.
Boxeador
A2This is the most common and standard term used to describe an athlete who practices boxing. It is formed by adding the suffix for doer or agent (-dor) to the name of the sport (boxe). It is the practical, everyday word used in casual conversation.
O boxeador treina todos os dias na academia local.
(The boxer trains every day at the local gym.)
Mike Tyson é o boxeador favorito do meu pai.
(Mike Tyson is my father's favorite boxer.)
Ela decidiu se tornar uma jogadora de futebol, não uma boxeadora.
(She decided to become a soccer player, not a boxer.)
O jovem boxeador venceu a luta por nocaute.
(The young boxer won the fight by knockout.)
Os luvas do boxeador devem ser aprovadas pelo árbitro.
(The boxer's gloves must be approved by the referee.)
Pugilista
B2This word comes from the Latin pugil (fighter). While it means the exact same thing as boxeador, it carries a slightly more formal or elevated tone. It is very frequently used in sports journalism, news reports, or medical contexts regarding the sport to avoid repeating the word boxeador too many times.
O famoso pugilista anunciou sua aposentadoria ontem.
(The famous boxer announced his retirement yesterday.)
É comum ver um pugilista com o nariz quebrado.
(It is common to see a pugilist with a broken nose.)
A técnica deste pugilista é muito superior à do seu oponente.
(This boxer's technique is far superior to that of his opponent.)
Muhammad Ali foi eleito o maior pugilista de todos os tempos.
(Muhammad Ali was voted the greatest boxer of all time.)
A dieta de um pugilista precisa ser muito rigorosa antes da pesagem.
(A boxer's diet needs to be very strict before the weigh-in.)
Summary
You can usually use boxeador and pugilista to mean exactly the same thing. Boxeador is the direct word linked to the sport name and fits any situation. Pugilista is a synonym often favored by commentators and writers to add variety to their vocabulary or to sound more professional.