Bro is a male youth subculture of "conventional guys' guys" who spend time partying in ways similar to each other. Although the popular image of bro lifestyle is associated with sports apparel and fraternities, it lacks a consistent definition. Most aspects vary regionally such as in California where it overlaps with surf culture. Oxford Dictionaries have noted that bros frequently self-identify with neologisms containing the word "bro" as a prefix or suffix.
Bro was originally an abbreviated form of "brother" but began to assume non-familial connotations in the 20th century. In this evolution, it was first used to refer to another man, such as a "guy" or "fellow", or sometimes, specifically, a black man. In these ways, it was semantically similar to the use of "brother". In the 1970s, bro came to refer to a male friend rather than just another man. The word became associated with young men, "conventional guys' guys" who spend time partying in ways similar to each other. Oxford Dictionaries identified the use of the term "bro" as the one "defining feature" of the changing cultural attributes of young manhood.
The applications of bro subculture correlate with neologisms that include the word. The word is used as a modifier for compound terms such as "brogrammer" and "curlbro". The word brah is used similarly, and is sometimes combined as "bro-brahs". Oxford Dictionaries wrote that the term "lends itself" to compounding and blending, with combinations such as "bro-hug" and "bro-step" and portmanteaux such as "bro-down", "bromance", and "brohemian". This creation of neologisms was called "portmanbros" by 2009. Oxford Dictionaries compared this trend to man- prefixes (e.g., man cave, mansplaining, manscaping) but noted that the bro portmanteaux subset refers to a smaller portion of masculinity. Oxford Dictionaries also noted that many of the terms were "stunt coinages" with little hope of widespread adoption. However, the term "bromance", whose first usage was recorded in a 2001 issue of TransWorld Surf, entered the Oxford English Dictionary. The term "bro-hug" was used at least eight times in The New York Times between 2010 and 2013 and "brogrammer" once became the center of Silicon Valley gender conversations. In comparison to the "hipster" modifier, Oxford Dictionaries called the "bro" modifier more playful, and responsible for making the subculture "ripe for (often self-inflicted) mockery".