semi-swear 

1.When somebody asks you if you sware but it is a situation that you can not 100% say you will not get mad, offened, or tell somebody what the person says.

2.When someone doesn't complete a sware like "YOU SON OF A" or cover up a word with astrics.

Person 1: Can i tell you a secret?
Person 2: Yeah
Person 1: Can you sware not to get mad?
Person 2: I semi-swear
Person 1: Ok, it's about your girlfriend
Person 2: Yeah?
Person 1: She is cheating on you with me
Person 2: YOU SON OF A *****
Person 1: But u swore!
Person 2: I SEMI SWORE YOU *******

semi-swear by Preston Michael January 2, 2006