Oh fuck! Fuck!!!! Fuck... 아 씨발! 씨발!!!! 씨발... Both words is same but there is a difference existing in the sexual circumstance. That "Oh fuck me yeah!!" is good to say in that circumstance but "아 씨발 나!!!" has no meaning. "씨발(Si-bal)" is from sexual sentence as "씹질할 놈" however, now, it doesn't include the meaning of sexual content. Just a speaking ill to someone. But, with friends, they use that for keeping their relationship.