Oppa (오빠), a korean word, means older brother, and can be used for several things;
For a girl to call an older male, to imply she trusts them.
For a girl to call an older male, to show respect.
For a girl to call an older male, in a flirtatious way.
This word's meaning can often be mistaken by daddy instead of older brother. Although it can be used in a flirtatious way, it isn't a way to call someone "daddy".
Also is what many ARMYs call the members of the k-pop band, BTS. I'm assuming in a flirtatious way.
The member Jungkook (the youngest) has a great dislike for being called oppa.
For a girl to call an older male, to imply she trusts them.
For a girl to call an older male, to show respect.
For a girl to call an older male, in a flirtatious way.
This word's meaning can often be mistaken by daddy instead of older brother. Although it can be used in a flirtatious way, it isn't a way to call someone "daddy".
Also is what many ARMYs call the members of the k-pop band, BTS. I'm assuming in a flirtatious way.
The member Jungkook (the youngest) has a great dislike for being called oppa.
Example 1:
Girl: Hey, oppa! Wanna hang out today?
Boy: Oh, sure.
Example 2:
Girl: Hey there, oppa~
Boy: *Flustered* ..oh, hi.
Bonus example:
Fan: JUNGKOOKIE OPPA!
Jungkook: *TRIGGERED* I A M N O T Y O U R O P P A
Girl: Hey, oppa! Wanna hang out today?
Boy: Oh, sure.
Example 2:
Girl: Hey there, oppa~
Boy: *Flustered* ..oh, hi.
Bonus example:
Fan: JUNGKOOKIE OPPA!
Jungkook: *TRIGGERED* I A M N O T Y O U R O P P A
by smolbeanjungkook June 29, 2018
Get the Oppamug. Australian slang, an either abbreviation of the word opposition or coppas, commenly used to refer to ones enemy gangs or police.
by DomesticConeAbuse March 18, 2020
Get the Oppasmug. Oppa comes from the words "opp" which means opposition in street slang. Oppa, however, relates to the term "Black Ops" which is a covert or clandestine operation by a government agency, a military unit or a paramilitary organization; it can include activities by private companies or groups. Someone who is under the Black Ops organisation is referred to as an "Oppa"
by glizzyfrompbm May 14, 2021
Get the Oppamug. by yeetboi555 July 24, 2019
Get the Oppamug. OPPA is an emote used to express frustration with something, as you can probably guess with the man smashing his keyboard
why the emote is used is in reference to XL, which is the abbreviation of Xiangling
Xiangling is usually taken as the basis for analysing how good a character is when talking about damage output and ease of use
as such, she gets mentioned so much that even mentioning her name is enough to trigger genshin players and move them to anger
so OPPA XL is basically used when XL is mentioned
the word AGANE (the incorrect spelling of again) is also used in conjunction at times as it's used to refer to her being mentioned all the time
why the emote is used is in reference to XL, which is the abbreviation of Xiangling
Xiangling is usually taken as the basis for analysing how good a character is when talking about damage output and ease of use
as such, she gets mentioned so much that even mentioning her name is enough to trigger genshin players and move them to anger
so OPPA XL is basically used when XL is mentioned
the word AGANE (the incorrect spelling of again) is also used in conjunction at times as it's used to refer to her being mentioned all the time
by Bacobowl July 12, 2022
Get the OPPA XLmug. 
Get the JungKook Oppamug. A person (particularly a non-Korean or mainly a non-Asian girl) who is obsessed with Korean men and is desperate to either be friends with them, be in a relationship with them, and or marry a them. They are also commonly known to overuse the word "oppa" (Korean word for a male that is older than you; term used by females) when talking not only about Korean males, but to other Asian men who happen to look Korean.
Guy 1: Dude this girl in my Korean class is a total oppa hunter.
Guy 2: Really? How so?
Guy 1: When I told her that I'm Korean she wouldn't stop calling me 'oppa' and then she wouldn't stop talking about her favorite K-POP groups and singers.
Guy 2: She sounds annoying.
Guy 1: You have no idea. She even called the Taiwanese guy in our class 'oppa'.
Guy 2: Is she even Asian?
Guy 1: Nah, she's white.
Guy 2: Really? How so?
Guy 1: When I told her that I'm Korean she wouldn't stop calling me 'oppa' and then she wouldn't stop talking about her favorite K-POP groups and singers.
Guy 2: She sounds annoying.
Guy 1: You have no idea. She even called the Taiwanese guy in our class 'oppa'.
Guy 2: Is she even Asian?
Guy 1: Nah, she's white.
by choiinsoo August 21, 2013
Get the Oppa Huntermug.