You can use the word OSS in many ways as seen in the picture above BUT in all seriousness ( LOL ) the true, real meaning is always something people ask and wonder about and as new people join BJJ it will never get out of style.
Some like it, some live by it, some hate it but it was, is and will always be part of our Martial Art. Undeniably so.
The word is explained here:
“How the greeting / salutation “Oss” came about
The famous “OSS” has many origins. The first definition of “OSS” as an abbrevition for Onegai Shimasu, which translates into a request, a solicitation, an invitation like “please”, “if you may” or “with your permission”, much used when inviting a partner to train.
The second definition of “OSS”, also known as “ossu” ( it doesn’t matter how you spell it in English), means Oshi Shinobu, which conveys the idea (the literal translation has nothing to do with the context) of “persevering when pushed”, or in other words, never give up, have determination, grit and withstand the most arduous of training. Carrying on without giving up, under all kinds of pressure – that’s the idea of inner strength so common in Asian culture.
Therefore, at the start of a fight, the martial artist will shout, invoke, emanate the “OSS”, as a way of letting this sentiment out. In many sources, “OSS” is defined as a manifestation of ki energy, or in other words, a different kiai (strength), indicating one is ready to fight.
According to Miyamoto Musashi, in the book “Go rin no sho” (Book of the five rings), the samurai would use three types of shouts: one before combat, the second during combat, when attacking, to muster greater strength (kiai), and the third after the fight, to celebrate victory or bemoan defeat.
“Oss”, beyond demonstrating strong spirit and determination before a fight, is also used to suggest or confirm a piece of information. Thus, whenever a Sensei asks or informs of something, the response is “OSS!” It is the response that will signify understanding or confirm understanding.”
– Excerpt from Gracie Magazine