OSS?

Oss! This a common acknowledgement used in martial arts academies and studios. Recently we hosted Prof.Terere who often used the term and expected it as a response or acknowledgement whern giving instruction. As not everyone has had experience with traditional martial arts I came across a cool explanation of the term and it's use from Gracie Mag.
Hope this helps.

"The famous "OSS" has many origins. The first definition of "OSS" is an abbreviation 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" means Oshi Shinobu, which conveys the idea (the literal translation has nothing to do with the context) of "persevering when pushed" 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 tout. 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 "五輪書, Go Rin No Sho", the samurai would use three types of shouts: One before combat, the second during combat, when attacking to muster great strength and the third after the fight, to celebrate victory.

"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 something, the response is "OSS!" it is the response that will confirm understanding."