What does 'oss' mean in Karate?

Answer 1

Osu is not a word used in Okinawan karate. The meaning has some rather militaristic type of strong assertiveness, masculinity and "we're going to kick butt" spirit in Japanese. It is out of place in many dojo and should never be used toward a Japanese person.

Answer 2

"Oss" is used as respectful greeting or acknowledgment/understanding of a command given by your sensei.