In my opinion you are only truely bisexual if you are attracted to both masculine and feminine characterstics(or both the cock and the cunt). But the human body is bisexual by default, although your preferences may not be. You will respond sexually to both sexes stimulating you. If you are attracted to the opposite gender, and those which look like the opposite gender, youre probably strait. I'd like to be truely bisexual myself, so at least I could enjoy masturbating to twice as much porn, but so far I haven't had much luck. I have only managed to be attracted to women and men who look like women. And I wouldn't even really say I am sexually attracted to those men, I just wanna cuddle with them... then again my explicit urge to fuck isn't that strong for either gender.