Budoka around the world say an expression that sounds like this, "Osss". They use it in response to an instructor's direction or when bowing or when entering or leaving a dojo. When I first started in the martial arts, I used to ask what, "Osss" meant, but no one knew. It was just something we did. I even remember asking some Japanese tourist that were riding a N.Y.C. subway next to me what it meant, and they didn't know either. So, I didn't give it a second though and kept on training and saying, "Osss".
I used to write it as Ooossss because Grandmaster Peter Urban (American Goju Karate) used to write it that way for his Blackbelt and Karate Illustrated magazine articles. Now we know that the Japanese word is spelled Osu. However, since the "u" is silent, spelling it Osu would be confusing for English speakers. So, I will take the onomatopoeia license of English and spell it as a sound--Oss or Ous.
May you endure all of your efforts. Thank you for visiting--Oss!
In 2008, I ran into an interview with Hirokazu Kanzawa sensei where he explained the meaning of "Osss". Apparently, it is made up of two Japanese words -- "O" and "Su". "O" means Push or Effort, and "Su" means to Endure. Therefore, when you say, "Osss", you are saying to endure your effort, or your hard work, or your success.