Maan Karate meaning

Maan karate is a martial art.
"Maan" gets translated into Deer (in Tamil)
"Karate", everyone knows it. Fighting without any weapon.

"Maan karate" here refers to act like a deer.
Rules include being flexible, sharp like a deer. In case of any danger, deer runs away and the same is suggested in this art too.
Hero running away from the threat/danger is the extract of the title, though the name can also be due to the art which was performed actually in the movie.