The word OSU is considered by many karateka, both Japanese and non-Japanese to be a crude word, not acceptable for use in the dojo. This is because it is interpreted as a contraction of “Ohayo gozaimasu” (a greeting), and through its use in the docks, barracks, bars and city back streets it is therefore the equivalent of “Waazzup man!”.
The OSU in Kyokushinkai and Shinkukai karate however does not have the same origin. It comes from the expression “Oshi shinobu” which means to push oneself to the limit of one’s ability and yet to continue, to persevere under pressure, and to endure.
It is used as a word of many meanings, expressing the willingness to strive against all odds, to persevere on the road to physical, mental, and spiritual strength, an expression of respect of ones seniors and responsibility to ones juniors.
It is pronounced “OSS!” with a long “O”, and not “Oosh” or “Oos” as is commonly heard outside of Japan.
In the Kyokushinkai and Shinkukai schools of karate it is also a greeting and can be used to replace words such as “yes”, “alright”, “good”, “I’ll do that” and “excuse me”. It is also used to mean “hello”, “goodbye”, “have patience with me”, “I’m trying”, “well done!” and just about anything else. Unlike many other karate styles, a student is never expected to say “yes sir” (Hai) when given a command in the Kyokushin and Shinkukai dojo, but to use the word “OSU” instead.
As students of karate, we are all expected to strive and develop this positive attitude (spirit) of perseverance, determination and respect for others in our training as well as in our daily life (i.e. business, work, studies etc). but you don’t have to be a karateka to have spirit Osu! Any competitor in the Para Olympics has it, probably more than any karateka, simply for not letting their physical incompleteness stop them doing their best. A parent, doing three jobs to feed his or her children and running a house has Osu!
If it is at all possible to express the philosophy of Shinkukai Karate in a single word, then “OSU” would be that word.
Shihan Neil Harrison, Original Shinkukai Karate